Monthly Archives: July 2022

When studying a complex system, scientists identify smaller pieces called subsystems that they can make sense of. By studying subsystems and the correlations between them, they reconstruct an understanding of the whole.

This approach has been used with great success to explain phenomena and develop applications in computing, cryptography and sensing based on quantum mechanicsthe physics of matter and energy at the scale of the atom or smaller. But this approach is limited to systems that operate in a world where time is absolute.

This description of subsystems falls short when describing scenarios that involve Einsteins theory of general relativity, where time is relative to an observers motion and tightly interwoven with space into a four-dimensional spacetime.

Now, a theoretical study co-authored byAlexander Smith, assistant professor of physics at Saint Anselm College and adjunct assistant professor at Dartmouth, and Shadi Ali Ahmad 22, proposes a new way to identify subsystems and correlations compatible with general relativity.

Theoretical physicists have long been striving to combine quantum mechanics and general relativity into a unified theory of quantum gravity. It is hoped that this work may be applied in developing a quantum description of spacetime, says Smith.

The results, published in April inPhysical Review Letters, build on previous work on a generalized notion of subsystems by the James Frank Family Professor of Physics Lorenza Violaand her collaborators. Instead of having composite building parts that are glued together into a larger system, subsystems should be thought of as directly arising from the observable properties one can measure, says Viola.

Quantum mechanics allows for correlations that are not consistent with our classical understanding of the world, says Smith, Viola and her collaborators gave us a new way to think about these unintuitive quantum correlations.

Smith, Ali Ahmad and their collaborators apply this idea to build a framework for identifying subsystems, which is consistent with relativity, and find that the notion of the subsystem is no longer rigid.

The way we partition a system is also relative. It depends on who is looking at it, says Smith. While their method currently applies to simple systems of several particles, the authors are working to generalize the framework to quantum field theory, which constitutes our most fundamental description of nature.

Several theoretical concepts that are driving the emerging understanding of quantum gravity have their origin in quantum information theorya relatively new field that studies how information in a quantum system can be analyzed and manipulated. Quantum information science has given us this whole new way to think about quantum mechanics itself, says Smith.

Working with Smith and other researchers, Ali Ahmad, a physics and mathematics major from Beirut, has used quantum information theory to study a number of different theoretical problems. Inprevious work, they were the first to examine how gravitational wavesripples in spacetime produced when massive astronomical objects (e.g. black holes) speed up to extreme levelsaffect entanglement between systems.Another projecttackled the question of how workthe measure of how much energy is transferred when a force acts on an objectcan be defined operationally at the quantum scale.

Smith says Ali Ahmad is one of the most driven to learn, hardworking and productive students he has encountered. Seeing Shadi develop his ability in theoretical physics over the past four years has been very rewarding, he says.

Ali Ahmad won the 2022 Gazzaniga Family Science Award, which recognizes scientific accomplishment of a graduating senior in the sciences. He is also the recipient of the Physics and Astronomy Chairs Prize.

Quantum information theory is a toolbox that I like to borrow from and use broadly, says Ali Ahmad. The promise of access to undergraduate research opportunities and funding was what drew him to Dartmouth, he says. Now a research fellow at Dartmouth, Ali Ahmad is wrapping up ongoing projects as he prepares to apply to graduate programs.

With classes as a springboard, he sought out research mentors in the physics and mathematics departments, collaborating with them on a wide range of research topics. Talking about science with people shapes the way you think, says Ali Ahmad, who already has three publications under his belt. I think it really sharpens your interests.

Read the original here:

Physics Major Works on a New Theory of Quantum Subsystems - Dartmouth News

The supermarket checkout scanner, the printer in your office, the pointer used in yesterdays meeting lasers are pretty much a part of everyday life now. You think about them very little, even as they do amazing things like instantly read barcodes or correct your nearsightedness via LASIK surgery.

But what is a laser, really? What makes them so special and so useful? Indeed, what makes a laser different from a simple lightbulb? The answers rest in the remarkable weirdness of quantum physics. Lasers are a quintessential quantum phenomenon.

The key question we have to deal with here is the interaction of light and matter. In classical physics, light is made of waves of electromagnetic energy traveling through space. These waves can be emitted or absorbed by accelerating electrically charged particles of matter. This is what happens in a radio tower: Electrical charges are accelerated up and down the tower to create the electromagnetic waves that travel through space to your car and let you listen to your station of choice.

At the turn of the century, scientists wanted to apply this classical idea to create models of atoms. They imagined an atom as a little solar system, with the positively charged protons at the center and the negatively charged electrons orbiting around them. If an electron emitted or absorbed some light, i.e. electromagnetic energy, it would speed up or slow down. But this model didnt hold. For one thing, there is always an acceleration happening when one thing orbits another this is called centripetal acceleration. So the electron in this classical model of the atom must always be emitting radiation as it orbits and thereby losing energy. That makes the orbit unstable. The electron would quickly fall onto the proton.

Niels Bohr got around this problem with a new model of the atom. In the Bohr model, an electron can only occupy a set of discrete orbits around the proton. These orbits were visualized like circular train tracks that the electrons rode as they circled about the proton. The farther out an orbit was from the proton, the more excited it was, and the more energy it held.

In the Bohr model, the emission and absorption of light was all about electrons jumping between these orbits. To emit light, an electron jumped from a higher orbit down to a lower orbit, emitting a packet of light energy called a photon. An electron could also jump from a lower orbit to a higher one if it absorbed one of these light packets. The wavelength of the light emitted or absorbed was directly related to the energy difference between the orbits.

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There was much quantum weirdness in all of this. If the electron was bound to these orbits, that meant it was never between them. It jumped from one location to the other without ever occupying the intervening space. Also, light was both a particle a photon that had a packet of energy and a wave spread out through space. How do you imagine that? While the Bohr model was only a first step, modern versions of the theory still feature discrete energy levels and photon wave-particle duality.

How does this relate to lasers? LASER stands for Light Amplification Through Stimulated Emission of Radiation. The ideas of amplification and stimulated emission in a laser are based on those specific energy levels of electrons in atoms.

To make a laser, you take some material and exploit its quantum energy levels.

The first step is to invert the population of the levels. Usually, most electrons will reside in the atoms lowest energy levels that is where they like to rest. But lasers rely on boosting most of the electrons to a higher, excited level also called an excited state. This is done using a pump that pushes the electrons up to a specific excited state. Then, as some of these electrons begin spontaneously falling down again, they emit a specific wavelength of light. These photons travel through the material and tickle other electrons in the excited state, stimulating them to jump down, and causing more photons of the same wavelength to be emitted. By placing mirrors at either end of the material, this process builds up until there is a nice, steady beam of photons that are all the same wavelength. Some fraction of synchronized photons then escapes through a hole in one of the mirrors. That is the beam you see coming from your laser pointer.

This is exactly what does not happen in a light bulb, where atoms in the heated filament have electrons jumping up and down chaotically between different levels. The photons they emit have a wide range of wavelengths, which causes their light to look white. It is only by exploiting the weird quantum levels of electrons in an atom, the weird quantum jumps between those levels, and finally, the weird wave-particle duality of light itself, that those amazing and very useful lasers come into being.

There is, of course, a lot more to this story. But the basic idea you want to remember next time youre at the grocery store check-out is simple. A world beyond your perception the nanoworld of atoms is incredibly different from the one you live in. Somehow, we humans have peered into that tiny realm and come back with a deep enough understanding to reshape the macroworld we inhabit.

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Lasers are weird and amazing - Big Think

MANOUSH ZOMORODI, HOST:

It's the TED Radio Hour from NPR. I'm a Manoush Zomorodi.

And if you've ever heard a song and instantly been transported back in time, you know the power of music to punctuate an event in your life or distill a moment in history. Musician Rosanne Cash calls this the rhythm and rhyme of memory. And she says it's the force behind her songwriting.

ROSANNE CASH: There's a mystery and a magic at the center of this process that's really undefinable and unexplainable. And when you touch that, you're touching something of the divine. It's this creative source.

ZOMORODI: That creative source has led her to record 15 albums over the past four decades and win four Grammy Awards. It also, she says, helped her accept the scrutiny that came with being the legendary Johnny Cash's daughter and, more recently, confront America's painful past, including her family's own role in that history.

R CASH: I often don't know what I feel or think. And I don't know how to process things. And I don't know what I want until I write about it.

ZOMORODI: On this episode, we explore the links between memory and music with singer, songwriter and musician Rosanne Cash, who is incredibly cool and funny and punctual.

Wait a minute, it's exactly 9 a.m. and we're both recording and ready to go.

R CASH: (Laughter).

ZOMORODI: How is that even possible?

R CASH: It's unheard of.

(SOUNDBITE OF SONG, "A FEATHER'S NOT A BIRD")

R CASH: (Singing) A stone is not a mountain, but a river runs through me.

ZOMORODI: And off we go.

Rosanne Cash, hello, and thank you so much for being here.

R CASH: Hi, Manoush. I'm thrilled to talk to you.

ZOMORODI: So, Rosanne, I have to imagine that as the daughter of Johnny Cash, there was probably a good amount of music in your life as a child. Was it something that was just everywhere? I mean, I know that your dad had his first single put out just a couple months after you were born.

R CASH: About a month, actually.

(SOUNDBITE OF SONG, "CRY, CRY, CRY")

JOHNNY CASH: (Singing) I wasted my time when I would try, try, try 'cause when the lights have lost their glow, you'll cry, cry, cry.

R CASH: Yeah. It was in the house all the time - and not just what my father was playing - you know, Jimmie Rodgers and Woody Guthrie and, you know, Hank Williams and all of the older country stars and Sister Rosetta Tharpe and the gospel and blues. All of that was around.

(SOUNDBITE OF SONG, "UP ABOVE MY HEAD")

SISTER ROSETTA THARPE: (Singing) Up above my head. Up above my head. I hear music in the air.

R CASH: But then when my dad was on the road, what my mother played was also incredibly influential. She loved Patsy Cline.

(SOUNDBITE OF SONG, "STRANGE")

PATSY CLINE: (Singing) Well I guess that I was just your puppet you held on a string.

R CASH: And then when I was old enough to discover the songs on the radio for myself, then it was the Beatles.

(SOUNDBITE OF SONG, "I SAW HER STANDING THERE")

THE BEATLES: (Singing) Well, she was just 17.

R CASH: I learned to love the Beatles and Patsy Cline and blues and Southern gospel and Marty Robbins and, you know, Crosby, Stills, Nash & Young. It was all swirling around.

ZOMORODI: In the talk you gave in 2021, which is called "The Rhythm And Rhyme Of Memory, Solitude And Community," you say that in your family there was a song for every loss, every celebration, every unspoken need, every longing. And I guess I would think, wow, that is a family that is great at communicating with each other. But that was not necessarily the case, right?

R CASH: No. Well, what you describe is the - if that was actually carried out, if that was actually something that was happening, the idea that we could sit down and go, this is how I'm feeling, and here's the song for it - no. What happened is that I found those songs for myself. They helped explain me to my selves, you know, that indefinable longing or sadness or melancholy or hope or loss or thrill. There were songs for every most nuanced expression of all of those emotions. There are songs for each one. And I was able to find them, you know?

There's something in my DNA that was attuned to that language. But the - my house was much more chaotic. I think that the - music is how I made sense of a lot of things, and it was my particular kind of special cave that I went into. You know, my father was a drug addict in my early years. My mother was not equipped to handle either a partner who was a drug addict or fame. And those are the two things that kind of permeated our household - and then my mother's anger and fear and grief about all of those things. So there was not a lot of room for other emotion.

And I think me and my sisters were - we didn't have anything explained to us. You know, they didn't talk to kids back then. There was no way they were going to sit down and say, look, your father's a drug addict, and here's what's happening. No. So the confusion and fear, you know? - and children think, oh, that's - this has to be my fault. It was complicated.

ZOMORODI: What were some of the ways that you coped with having a dad who was so famous?

R CASH: The thing is, is that I my family was so abnormal that I looked for, what did normal families do? I loved the "Little House On The Prairie" series because, you know, the washing was on Monday, and the baking was on Tuesday. And you did this and you didn't wear this, and you didn't speak like this. And I thought, OK, that's normal. And I wanted to create my own sense of normalcy.

ZOMORODI: So if you didn't live a normal childhood and you were looking for normalcy, what are some of your first memories, or what did you think you would grow up to become?

R CASH: Oh, I knew I would be a writer. I had a dream when I was 13 years old, and it was of my mother and my grandmother. And they were sitting at a card table. And they were vacant, just vacant behind the eyes and rote in their actions. And they kept putting cards slowly on the table to each other. And I woke up in a sweat at 13. And I said to myself, I will never be a card player. And I wrote my dad a letter - my dad was on the road - about my - those impulses. I didn't want to live in that kind of deadening routine. I wanted to do something that touched the divine. I didn't use those words at that time. But he wrote me back, and he said, I see that you see as I see.

ZOMORODI: Wow.

R CASH: And I held on to that. And I realized that there was a template for me to be who I was in the world, and it wasn't to copy, but it was to explore and find myself. And in some ways, my dad and I had a simpler relationship than I had with my mother. She saw that I was - there was some kind of DNA thread that was similar to my dad's, that I was an artist. And I think she saw that from a young age, and it terrified her.

ZOMORODI: So you started writing pretty early on.

R CASH: Yeah. Well, I did write poetry starting from about the age of 8 or 9. Rhyme and language were already - even from the time I was 3, my mother said, you asked what every word said and what it meant. So I was writing poetry all through my teens. And then at some point - this babysitter I had wrote to me, you know, like 10, 15 years ago and said, I babysat you. And I remember you said, how do you put poetry to music? And I thought to myself, why was I asking her?

(LAUGHTER)

R CASH: I had a better authority in my own house. But yeah, that's what happened, is that when I learned to play guitar, I started writing songs. And that was about age 18.

ZOMORODI: You tell a story in your TED Talk about some writing you did when you were younger - this phrase that you came up with that ended up revisiting you later in life and really influencing you.

R CASH: Yeah. I was in my mid-30s, and I was working on a song. And my mom at the same time across the country was going through my school papers and drawings and, you know, things from childhood of mine that she'd saved. And she sent me this whole box. And I was leafing through the box, and I came across this paper I had done in seventh grade on metaphors and similes.

And I looked at this paper, and I - it suddenly just washed over me. The thrill I had felt in doing that paper was the first time that I had ever been excited about anything that they had asked me to do in Catholic school. And there was this metaphor I had written. A lonely road is a bodyguard. This is a beautiful metaphor that I wrote at 12 years old. And it really moved me and struck me. And I just took that line and put it right in the song I was writing. The song's called "Sleeping In Paris."

ZOMORODI: Here's Rosanne Cash performing on the TED stage.

(SOUNDBITE OF TED TALK)

R CASH: (Singing) I'll send the angels to watch over you tonight, and you send them right back to me. A lonely road is a bodyguard if we really want it to be.

A lonely road is a bodyguard. What did it mean? I had even pasted a picture of this empty road next to the line. So my 12-year-old waved at me across the decades saying that who I was was who I would become. As painful as that was then and as it still can be painful now, I knew what she was telling me - that solitude can protect the seeds of creativity and that loneliness contains a priceless gift. If we can tolerate the initial discomfort and avoid the seduction of despair, we're all just radios hoping to pick up each other's signals. And some of those signals have a backbeat and a melody, and they're universal. And music can unlock a frozen memory that melts into the seeds of our creativity. And the reverse is also true. A memory can unlock a song that's waiting to be written.

ZOMORODI: When we come back, more with Rosanne Cash, including a recent revelation about her mother that adds a twist to her family's history. I'm Manoush Zomorodi, and you're listening to the TED Radio Hour from NPR. Stay with us.

(SOUNDBITE OF SONG, "DANCE WITH THE TIGER")

R CASH: (Singing) Of just how alone are all who live here.

ZOMORODI: It's the TED Radio Hour from NPR. I'm Manoush Zomorodi, and with me for the hour is Rosanne Cash.

Hi, Rosanne.

R CASH: Hi, Manoush.

ZOMORODI: So we were talking about your dad, Johnny Cash. In the '60s, he moved your family from Tennessee to California. But as you said, it was kind of a tough childhood. As your father's success exploded, your parents' relationship really suffered. And I think most people know more about your dad's second wife, June Carter. But tell us about your mom, his first wife, Vivian, because she was a quiet but intense character.

R CASH: She wasn't very quiet at home.

(LAUGHTER)

R CASH: She was very intense. She's Sicilian, you know? She was very private and was not equipped to deal with my dad's sudden fame - explosive fame - and then his subsequent drug addiction. You know, in the '60s, it was like - he would have to drive 200 miles and do three shows a night, you know, on these tours. And at some point, someone gave a pill to him and said, take this. It'll keep you awake. Take this, and it'll help you sleep afterwards. And then that was it.

So my mom was not prepared for that. And then, you know, her - the template she had later on - when I went into, you know, became a songwriter and she realized that this was going to be my life path, she - her template for that was, oh, you get on drugs. You get divorced. Your family falls apart. You're never home, you know? And she was terrified that that's - was going to be my life.

ZOMORODI: Did you reassure her and say, no, I've learned from what not to do?

R CASH: No. I was not in the business of reassuring my mom anything at the age of 18.

(LAUGHTER)

R CASH: I just wanted to get away.

ZOMORODI: Just to step back for a second, in the beginning of your parents' relationship, they were madly in love.

R CASH: Absolutely. My dad was in the Air Force for three years. And my sisters and I have 1,000 letters they wrote to each other.

ZOMORODI: Wow.

R CASH: Yeah.

ZOMORODI: That's crazy - a thousand. And is he saying, like, I'm going to be a big musical superstar?

R CASH: No, he was - it was mostly besotted teenage love. You know...

(SOUNDBITE OF ARCHIVED RECORDING)

J CASH: I do, Vivian. I love you very much. I love you more than anything in the world. We'll be together soon.

R CASH: My darling, my darling, my darling, and then, you know, he would throw in, I bought this record. I bought a cheap guitar. I have a little band with two of the other, you know, Air Force guys. And so there were these sprinklings of what was being seeded in him at that time.

ZOMORODI: And so there was this period where your parents were really happy.

R CASH: Oh, yeah - I mean, until I was about 6, I think. You know, it was great. They were in love. They were building a life together. Like you said, we moved to California when I was 3 from Memphis. And then things started falling apart.

ZOMORODI: I had read the story - I knew in the history books that in 1965 your father was arrested in Texas for drug possession. But I didn't know the story that your mom went down to get him out of jail and that there's a famous photo that was taken as they left the courthouse. And the public had, I mean, outrageous reaction to this photo. Can you explain what happened?

R CASH: Well, it was a, you know, a photo in the newspaper - not very pixelated, as it was back then. And it was dark. And my mother's features are Sicilian. And it appeared that she was African American. And there was this outcry that my father had married a Black woman. And the Ku Klux Klan started this campaign against my father to ban his records. And, you know, they excoriated him in the press. And it was this kind of - it got very intense and scary. And I didn't know what this was all about. But it was very frightening.

And he had to - he wrote this letter, you know, saying that my mother was Italian. And, you know, this went on for a while. And my mother was, like I said, so private. And she was extremely embarrassed by this attention - you know, something about her appearance or about her history or her race. And that was incredibly hard for her to process. It was too much attention and in the wrong way.

ZOMORODI: And there is actually another layer to this story, because your mother always believed that she came from an Italian American family, but you recently learned that there actually is some African heritage, too.

R CASH: It's so fascinating. I did "Finding Your Roots" a few years ago. And my mother's paternal side was, indeed, 100% Sicilian. They - you know, her grandparents immigrated from Sicily in the late 1900s and opened a store in San Antonio. All of this is well documented. And - but it turns out on her maternal side, whose history goes back deep in America, that in the 1840s there was a freed slave married to - actually, I don't know if they could get married, but they were living as man and wife in Alabama in the 1840s. They had nine children together. And one of those children is my grandmother's - my maternal grandmother's - direct ancestor.

ZOMORODI: Yeah. It's an amazing coda to this chapter in your family's history. Was it on your mind when you wrote the song "The Killing Fields"? You sing about your family's Southern roots and the history there of lynchings and racism in the South. It is haunting.

R CASH: Yeah. So writing "The Killing Fields" was a slow awakening. And I do not claim to be awakened about race and about the suffering of African Americans and about the history of slavery. But I am - I want to be awakened about it.

(SOUNDBITE OF SONG, "THE KILLING FIELDS")

R CASH: (Singing) There was cotton on the killing fields. It blows down through the years. It sticks to me just like a burn, fills my eyes and ears. And all that came before me...

And I had already been thinking about race. My grandfather - Cash - had a deep thread of racism running through him - you know, Arkansas farmer. And he was not well educated. And I'm not making excuses for him. It was a - it's a very painful thing to acknowledge about him. But I had been involved with the restoration of my dad's boyhood home in Arkansas for the past 12 years, 14 years. And going to Arkansas a lot, I became more aware of the really dark, dark history of racism and violence in Arkansas.

At around the same time, I was doing a show at Dockery Farms in Mississippi, which is really one of the birthplaces of the blues. It was a cotton farm where some of the great blues artists - Howlin' Wolf and Charley Patton - had picked cotton in the day and played guitar and music and juke joints at night. So doing this show, there was an after-party, all white people at the after-party and this nearly 90-year-old Black man playing blues harp with a guitarist - a white guitarist - at the after-party while the white people were milling around. And I kept looking at him all night.

And I went over to him after the party to say thank you so much, you know? That was so beautiful. Really appreciate you coming and playing. And he said, oh, I just want to tell you that when I was out behind the plow in the fields, that we had a radio sitting on the porch. And whenever your daddy came on the radio in the '50s, I would run over to listen to him. And I started weeping. I was thinking about my racist grandfather across the river in Arkansas behind the same kind of plow. And I realized that everything I do musically, creatively - that in some ways there's a thread that goes back to that Black man behind the plow in Mississippi musically and that white man behind the plow in Arkansas. And I started thinking about the threads you have to break in your life - the ones you bind, the ones you break.

(SOUNDBITE OF MUSIC)

ZOMORODI: OK. So that reminds me of another story you tell in your TED Talk about your grandmother, Carrie Cash, and what it was like to be a woman in the South - the American South - a century or so ago.

R CASH: Yeah. So she had seven children - one who died when he was 14. But she gave birth at home with the assistance of a doctor who came by in a horse-and-buggy to check on her. One of her labors - she was in labor for three days - he came by on a horse-and-buggy to check on her every day, once a day and pulled two aspirin from his pocket to give her. It was the same pocket in which he kept his fishing worms.

ZOMORODI: Wow.

R CASH: I know (laughter).

ZOMORODI: Here's Rosanne Cash again on the TED stage.

(SOUNDBITE OF TED TALK)

R CASH: I read once that every time an old woman dies, a library disappears. And before her library disappeared, I tuned in to my grandmother's signals and gleaned her tenacity, which I borrowed, and her long suffering and her life of constant work with seven children - six of whom made it to adulthood - in a house without electricity in the sweltering cotton fields. And I wrote these words about her.

(SOUNDBITE OF SONG, "THE SUNKEN LANDS")

R CASH: (Singing) Five cans of paint in the empty fields, and the dust reveals. And the children cry. The work never ends. There's not a single friend. Who will hold her hand in the sunken lands? And the mud and tears melt the cotton bolls. It's a heavy toll - oh, oh. His words are cruel, and they sting like fire, like the devil's choir - oh, oh. But who will hold her hand in the sunken lands? The river rises, and she sails away. But she could never stay - oh, oh. Now her work is done in the sunken lands. There's five empty cans.

(APPLAUSE)

Read more:

Rosanne Cash Reflects on Her Life and Legacy - NPR

The worlds top physicists will gather in Vancouver this August to launch a Quantum Gravity Institute that could significantly advance our understanding of physics and gravity.

The goal is to discover the theory of quantum gravity, one of sciences greatest mysteries.

Discovering the theory of quantum gravity could lead to the possibility of time travel, new quantum devices, or even massive new energy resources that produce clean energy and help us address climate change, said Philip Stamp, a professor at the University of British Columbia.

The conference will take place between Aug. 15-19, and will welcome two dozen of the worlds top physicists, including Nobel Laureates Jim Peebles, Sir Roger Penrose and Kip Thorne who is well known for developing the original idea for the 2014 film Interstellar.

For roughly 100 years, physics has been based on Einsteins theory of relativity and quantum mechanics.

The theory of relativity has helped us understand the cosmos, leading to space travel and technology like atomic clocks, which govern GPS systems. Quantum mechanics is responsible for the electronics, lasers, computers, cell phones and plastics that support modern transportation, communications, medicine, agriculture and energy systems.

The two theories have provided countless breakthroughs but are seemingly contradictory the theory of quantum gravity is meant to be the bridge between these two theories.

The potential long-term ramifications of this discovery are so incredible that life on earth 100 years from now could look as miraculous to us now as todays technology would have seemed to people living 100 years ago, Stamp said.

The conference will be open to the public on Aug. 17 and provide a once-in-a-lifetime opportunity to learn from the worlds pre-eminent physicists.

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Worlds top physicists to be in B.C. this summer to bring down sciences greatest mystery - Nelson Star

About the Centre for Quantum Technologies

The Centre for Quantum Technologies (CQT) is a research centre of excellence in Singapore. It brings together physicists, computer scientists and engineers to do basic research on quantum physics and to build devices based on quantum phenomena. Experts in this new discipline of quantum technologies are applying their discoveries in computing, communications, and sensing.

CQT is hosted by the National University of Singapore and also has staff at Nanyang Technological University. With some 180 researchers and students, it offers a friendly and international work environment.

Learn more about CQT atwww.quantumlah.org

Job Description

The candidate will conduct research on the classical and quantum complexity of submodularfunction minimization. Both the classical and quantum query complexities of this problemremain wide open. On the classical side the best upper bound is O(n^2) and the best lowerbound is Omega(n * log n). The quantum side is even more wide open, with no non-triviallower bound known, and also no general upper bound known better than the classical one.The successful candidate will investigate these questions with a special emphasis ondesigning new quantum algorithms for submodular function minimization.

Job Requirements

PhD in computer science or related field and a strong track record of research intheoretical computer science.

Covid-19 Message

At NUS, the health and safety of our staff and students are one of our utmost priorities, and COVID-vaccination supports our commitment to ensure the safety of our community and to make NUS as safe and welcoming as possible. Many of our roles require a significant amount of physical interactions with students/staff/public members. Even for job roles that may be performed remotely, there will be instances where on-campus presence is required.

Taking into consideration the health and well-being of our staff and students and to better protect everyone in the campus, applicants are strongly encouraged to have themselves fully COVID-19 vaccinated to secure successful employment with NUS.

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Visiting Research Associate Professor, Centre For Quantum Technologies job with NATIONAL UNIVERSITY OF SINGAPORE | 302907 - Times Higher Education

Australian scientists are making strides towards solving one of the greatest mysteries of the universe: the nature of invisible dark matter.

The ORGAN Experiment, Australias first major dark matter detector, recently completed a search for a hypothetical particle called an axiona popular candidate among theories that try to explain dark matter.

ORGAN has placed new limits on the possible characteristics of axions and thus helped narrow the search for them. But before we get ahead of ourselves

About 14 billion years ago, all the little pieces of matterthe fundamental particles that would later become you, the planet, and the galaxywere compressed into one very dense, hot region.

Then the Big Bang happened and everything flew apart. The particles combined into atoms, which eventually clumped together to make stars, which exploded and created all kinds of exotic matter.

After a few billion years came Earth, which was eventually crawling with little things called humans. Cool story, right? Turns out its not the whole story; its not even half.

People, planets, stars, and galaxies are all made of regular matter. But we know regular matter makes up just one-sixth of all the matter in the universe.

The rest is made of what we call dark matter. Its name tells you almost everything we know about it. It doesnt emit light (so we call it dark), and it has mass (so we call it matter).

When we observe the way things move in space, we find time and again that we cant explain our observations if we consider only what we can see.

Spinning galaxies are a great example. Most galaxies spin at speeds that cant be explained by the gravitational pull from visible matter alone.

So there must be dark matter in these galaxies, providing extra gravity and allowing them to spin fasterwithout parts being flung off into space. We think dark matter literally holds galaxies together.

The Bullet Cluster is a massive cluster of galaxies which has been interpreted as being strong evidence for the existence of dark matter. Image Credit: NASA

So there must be an enormous amount of dark matter in the universe, pulling on all the things we can see. Its passing through you, too, like some kind of cosmic ghost. You just cant feel it.

Many scientists believe dark matter could be composed of hypothetical particles called axions. Axions were originally proposed as part of a solution to another major problem in particle physics called the strong CP problem (which we could write a whole article about).

Anyway, after the axion was proposed, scientists realized the particle could also make up dark matter under certain conditions. Thats because axions are expected to have very weak interactions with regular matter, but still have some mass: the two conditions needed for dark matter.

So how do you go about searching for axions?

Well, since dark matter is thought to be all around us, we can build detectors right here on Earth. And, luckily, the theory that predicts axions also predicts that axions can convert into photons (particles of light) under the right conditions.

This is good news, because were great at detecting photons. And this is exactly what ORGAN does. It engineers the correct conditions for axion-photon conversion and looks for weak photon signalslittle flashes of light generated by dark matter passing through the detector.

This kind of experiment is called an axion haloscope and was first proposed in the 1980s. There are a few in the world today, each one slightly different in important ways.

The ORGAN Experiments main detector. A small copper cylinder called a resonant cavity traps photons generated during dark matter conversion. The cylinder is bolted to a dilution refrigerator which cools the experiment to very low temperatures. Image Credit: Author provided

An axion is believed to convert into a photon in the presence of a strong magnetic field. In a typical haloscope, we generate this magnetic field using a big electromagnet called a superconducting solenoid.

Inside the magnetic field we place one or several hollow chambers of metal, which are meant to trap the photons and cause them to bounce around inside, making them easier to detect.

However, there is one hiccup. Everything that has a temperature constantly emits small random flashes of light (which is why thermal imaging cameras work). These random emissions, or noise, make it harder to detect the faint dark matter signals were looking for.

To work around this, weve placed our resonator in a dilution refrigerator. This fancy fridge cools the experiment to cryogenic temperatures, about 273C, which greatly reduces the noise.

The colder the experiment is, the better we can listen for faint photons produced during dark matter conversion.

An axion of a certain mass will convert into a photon of a certain frequency, or color. But since the mass of axions is unknown, experiments must target their search to different regions, focusing on those where dark matter is considered more likely to exist.

If no dark matter signal is found, then either the experiment is not sensitive enough to hear the signal above the noise, or theres no dark matter in the corresponding axion mass region.

When this happens, we set an exclusion limitwhich is just a way of saying we didnt find any dark matter in this mass range, to this level of sensitivity. This tells the rest of the dark matter research community to direct their searches elsewhere.

ORGAN is the most sensitive experiment in its targeted frequency range. Its recent run detected no dark matter signals. This result has set an important exclusion limit on the possible characteristics of axions.

This is the first phase of a multi-year plan to search for axions. Were currently preparing the next experiment, which will be more sensitive and target a new, as-yet-unexplored mass range.

Well, for one, we know from history that when we invest in fundamental physics, we end up developing important technologies. For instance, all modern computing relies on our understanding of quantum mechanics.

We never would have discovered electricity, or radio waves, if we didnt pursue things that, at the time, appeared to be strange physical phenomena beyond our understanding. Dark matter is the same.

Consider everything humans have accomplished by understanding just one-sixth of the matter in the universeand imagine what we could do if we unlocked the rest.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Image Credit: Illustris Collaboration

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Scientists Hunt for an Elusive Particle to Unlock the Mystery of Dark Matter - Singularity Hub

Most assume that matter is fundamental, and that consciousness arises out of the complexity of matter. But Nobel Prize winning quantum physicist Erwin Schrdinger does not share that assumption. For him, the universe contains a single mind, writes Robert Prentner and Donald D. Hoffman.

In February 1943, Erwin Schrdinger, quantum physicist and Nobel laureate (sharing his prize with Paul Dirac and Werner Heisenberg), gave a series of lectures at Trinity College Dublin, which later turned into his book What is life? [1]. This work has been highly influential for a generation of molecular biologists such as Francis Crick, one of the discoverers of DNA. Less known perhaps is the fact that during his whole life Schrdinger was an ardent reader of philosophy from the East and West. From the 1950s on, when Schrdinger ceased to actively work on the physics of his time, he focused more on wider philosophical and ethical issues related to science. Back then, his conferences always ended with what he jokingly called the second Schrdinger equation: Atman = Brahman, the Indian doctrine of identity.

The present article investigates some of these ideas and gives them a reading in terms of a recent theory of consciousness. We believe that, just as Schrdingers ideas on the physical basis of life have inspired groundbreaking work in molecular biology, his ideas on mind and reality might inspire groundbreaking work in understanding the nature of consciousness and its relation to physics.

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Early on, Schrdinger expressed the conviction that metaphysics does not come after physics, but inevitably precedes it. Metaphysics is not a deductive affair but a speculative one.

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In 1925, just a few months before Schrdinger discovered the most basic equation of quantum mechanics, he wrote down the first sketches of the ideas that he would later develop more thoroughly in Mind and Matter. Already then, his thoughts on technical matters were inspired by what he took to be greater metaphysical (religious) questions. Early on, Schrdinger expressed the conviction that metaphysics does not come after physics, but inevitably precedes it. Metaphysics is not a deductive affair but a speculative one.

The many meanings of Schrdinger's catRead more One such speculative assumption (which can neither be proven nor disproven) is the one that there exists an external (mind-independent) world. Another one is the assumption that there exist separate minds. For both claims, according to Schrdinger, we cannot get any empirical evidence: how could we step out of our own experience to check them? But both create insurmountable problems. The first creates the problem of how to think about the relation between these two types of realities (mind-matter). Why does it appear (according to our best science) that we live in a purely physical world devoid of qualities? The second creates the problem of how to think about the relation between different minds (mind-mind). Why and how are we different from each other? Schrdinger believed that there is an elegant way to dissolve both of these problems by starting with an alternative metaphysical assumption. He did not endorse traditional Western views that go under the names of reductive materialism and subjective idealism, but he found inspiration in non-Western, particularly Indian philosophies.

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We are all but aspects of one single mind that forms the essence of reality.

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His second Schrdinger equation refers to an old staple of Indian philosophy according to which the self (Atman) is identical to the ultimate reality of the universe (Brahman), which forms a central part of the teachings of the Advaita Vednta. Schrdinger was quick to add that this self must not be conflated with the individual self but rather refers to a cosmic, universal entity of which individual selves are mere aspects.

A metaphor that Schrdinger liked to invoke to illustrate this idea is the one of a crystal that creates a multitude of colors (individual selves) by refracting light (standing for the cosmic self that is equal to the essence of the universe). We are all but aspects of one single mind that forms the essence of reality. He also referred to this as the doctrine of identity. Accordingly, a non-dual form of consciousness, which must not be conflated with any of its single aspects, grounds the refutation of the (merely apparent) distinction into separate selves that inhabit a single world.

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Not only has none of us ever experienced more than one consciousness, but there is also no trace of circumstantial evidence of this ever happening anywhere in the world.

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Schrdinger drew remarkable consequences from this. For example, he believed that any man is the same as any other man that lived before him. In his early essay Seek for the Road, he writes about looking into the mountains before him. Thousands of years ago, other men similarly enjoyed this view. But why should one assume that oneself is distinct from these previous men? Is there any scientific fact that could distinguish your experience from another mans? What makes you you and not someone else? Similarly as John Wheeler once assumed that there is really only one electron in the universe, Schrdinger assumed that there really is only one mind. Schrdinger thought this is supported by the empirical fact that consciousness is never experienced in the plural, only in the singular. Not only has none of us ever experienced more than one consciousness, but there is also no trace of circumstantial evidence of this ever happening anywhere in the world. [7]

In the contemporary scientific study of consciousness, many scholars try to circumvent the question of how and why matter gives rise to conscious experience by asking why there seems to be a hard problem in the first place (when there is in fact none): consciousness is an illusionary story that some physical systems equipped with brains tell themselves. While Schrdinger was far from accepting an illusionary stance about the reality of consciousness, in a very similar vein he asks why it seems as if there were a multiplicity of minds, where there is just one mind (the Atman=Brahman): the existence of many separate minds is an illusionary story that confused individuals would tell themselves. Thinking otherwise leads to the false belief that we are in some sense fundamentally isolated, rather than realizing that we are always connected with other beings (and ultimately also with what we now call non-living matter). Unlike in the hard problem case, there is no empirical evidence to suggest our initial belief is real.

An important characteristic of the way Schrdinger approached metaphysical and philosophical teachings was his prudence to uphold a rational and scientific methodology. The doctrine of identity cannot be adopted uncritically. We need to incorporate the doctrine into our best science, not throw our best science overboard. In other words, we should adopt a new metaphysics but keep with the scientific method. Our scientific theories need a bit of blood transfusion from Eastern thought [but] transfusions always need great precaution to prevent clotting. We do not wish to lose the logical precision that our scientific thought has reached, and that is unparalleled anywhere at any epoch. [8]

What Schrdinger sought, what he would have appreciated the most, is a scientific approach to studying consciousness with mathematical precision. An important constraint following from the doctrine of identity for any such theory of consciousness would be that it, in its very basic structure, acknowledges that individual conscious beings are (i) aspects of a higher, unifying agent (rather than being disconnected individuals), and (ii) that the entire collection of such beings constitutes the ultimate nature of reality (rather than being just one among many things such as electrons, rocks, or brains.)

Schrdinger desired a radically monist-theory that acknowledges the reality of consciousness. Given the current theoretical landscape in the study of consciousness, the theory of conscious agents [9] seems to fit best with these requirements. It aims for a precise, crisp formulation of what consciousness does, and it proposes that any combination of two or more conscious agents is itself another agent. It also seems to be compatible with the idea that the entire collection of agents constitutes the nature of reality, though this requires the theory to come up with a model of how the physical world can arise (and be nothing apart) from this collection.

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According to the theory of conscious agents, the idea of fundamentally separated selves is a useful fiction that arises only if we conflate what we see on the interface with the true reality of non-dual consciousness.

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How could this be so? Schrdinger relied on a couple of arguments that have been raised previously in philosophy (e.g. by Kant) but his position boils down to this: what we call the physical world is the result of a process that Schrdinger called objectivation, i.e. the transformation of the one self-world (Atman=Brahman) into something that can be readily conceptualized and studied objectively, hence something that is fully void of subjective qualities. In the theory of conscious agents this amounts to the creation of interfaces. Such interfaces simplify what is going on in order to allow you to act efficiently. Good interfaces hide complexity. They do not let you see reality as it is but only as it is useful to you. What you call the physical world is merely a highly-simplified representation of non-dual consciousness.

This physical world also appears to harbor a multitude of subjects directed at it. It is the very same process of objectivation, which led to the false impression of an autonomous physical world, that also leads to the fallacy of assuming different forms of consciousness inhabiting different bodies. The quick fix of adding mental properties to a non-mental world would not be able to really solve the problems mentioned earlier. Where to put them? Do we need to label them with a tag saying individual x? But then, why are you you and not someone else? How to combine one set of subjects into a higher one? But those problems can be circumvented by never giving in to the metaphysical assumption of the existence of one physical world that is opposed to many separated selves in the first place. According to the theory of conscious agents, the idea of fundamentally separated selves is a useful fiction that arises only if we conflate what we see on the interface with the true reality of non-dual consciousness.

The theory of conscious agents proposes an interesting answer to Schrdingers questions. Why does it appear that we are living in a physical world without qualities? Why and how are we different from each other? Because the dynamics of conscious agents results in the creation of interfaces that hide the true character of reality. We are the same, yet we can appear as different. From one perspective all agents combine into a single one which equals a (single) world. From a different perspective, this single agent is equal to a network of distinct agents that all inhabit their own worlds. Which perspective we choose, depends on what we want to explain.

References

[1] E. Schrdinger. What is Life? The Physical Aspect of the Living Cell, Cambridge University Press, Cambridge, 1944.

[2] M. Bitbol. Schrdinger and Indian Philosophy, in: Cahiers du service culturel de lambassade de France en Inde, Allahabad, 1999.

[3, 7, 8] E. Schrdinger. Mind and Matter, Cambridge University Press, Cambridge, 1958.

[4,5] E. Schrdinger. Seek for the Road, in: My View of the World, Cambridge University Press, Cambridge, 1963.

[6] R. Feynman. The Development of the Space-Time View of Quantum Electrodynamics. Nobel Lecture, 1965.

[9] D.D. Hoffman & C. Prakash. Objects of Consciousness, Frontiers in Psychology, 5: 577, 2014.

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