Daily Archives: May 9, 2021

May 4, 2021

Quantum science has the potential to revolutionize modern technology with more efficient computers, communication, and sensing devices. But challenges remain in achieving these technological goals, especially when it comes to effectively transferring information in quantum systems.

A regular computer consists of billions of transistors, called bits. Quantum computers, on the other hand, are based on quantum bits, also known as qubits, which can be made from a single electron.

Unlike ordinary transistors, which can be either 0 (off) or 1 (on), qubits can be both 0 and 1 at the same time. The ability of individual qubits to occupy these so-called superposition states, where they are in multiple states simultaneously, underlies the great potential of quantum computers. Just like ordinary computers, however, quantum computers need a way to transfer quantum information between distant qubitsand that presents a major experimental challenge.

In a series of papers published in Nature Communications, researchers at the University of Rochester, including John Nichol, an assistant professor of physics and astronomy, and graduate students Yadav Kandel and Haifeng Qiao, the lead authors of the papers, report major strides in enhancing quantum computing by improving the transfer of information between electrons in quantum systems.

In one paper, the researchers demonstrated a route of transferring information between qubits, called adiabatic quantum state transfer (AQT), for the first time with electron-spin qubits. Unlike most methods of transferring information between qubits, which rely on carefully tuned electric or magnetic-field pulses, AQT isnt as affected by pulse errors and noise.

To envision how AQT works, imagine you are driving your car and want to park it. If you dont hit your brakes at the proper time, the car wont be where you want it, with potential negative consequences. In this sense, the control pulsesthe gas and brake pedalsto the car must be tuned carefully. AQT is different in that it doesnt really matter how long you press the pedals or how hard you press them: the car will always end up in the right spot. As a result, AQT has the potential to improve the transfer of information between qubits, which is essential for quantum networking and error correction.

The researchers demonstrated AQTs effectiveness by exploiting entanglementone of the basic concepts of quantum physics in which the properties of one particle affect the properties of another, even when the particles are separated by a large distance. The researchers were able to use AQT to transfer one electrons quantum spin state across a chain of four electrons in semiconductor quantum dotstiny, nanoscale semiconductors with remarkable properties. This is the longest chain over which a spin state has ever been transferred, tying the record set by the researchers in a previous Nature paper.

Because AQT is robust against pulse errors and noise, and because of its major potential applications in quantum computing, this demonstration is a key milestone for quantum computing with spin qubits, Nichol says.

In a second paper, the researchers demonstrated another technique of transferring information between qubits, using an exotic state of matter called time crystals. A time crystal is a strange state of matter in which interactions between the particles that make up the crystal can stabilize oscillations of the system in time indefinitely. Imagine a clock that keeps ticking forever; the pendulum of the clock oscillates in time, much like the oscillating time crystal.

By implementing a series of electric-field pulses on electrons, the researchers were able to create a state similar to a time crystal. They found that they could then exploit this state to improve the transfer of an electrons spin state in a chain of semiconductor quantum dots.

Our work takes the first steps toward showing how strange and exotic states of matter, like time crystals, can potentially by used for quantum information processing applications, such as transferring information between qubits, Nichol says. We also theoretically show how this scenario can implement other single- and multi-qubit operations that could be used to improve the performance of quantum computers.

Both AQT and time crystals, while different, could be used simultaneously with quantum computing systems to improve performance.

These two results illustrate the strange and interesting ways that quantum physics allows for information to be sent from one place to another, which is one of the main challenges in constructing viable quantum computers and networks, Nichol says.

Tags: Arts and Sciences, Department of Physics and Astronomy, John Nichol, quantum computing, quantum physics

Category: Science & Technology

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Researchers confront major hurdle in quantum computing - University of Rochester

In quantum physics, Schrdingers cat refers to a thought experiment where a cat is simultaneously both alive and dead. But law is binarya statement is either true or false; a litigant either wins or loses; and a patent is either valid or invalid. Or is it?

In a fascinating 2019 ruling in Sanofi-Aventis v. Mylan, the federal district court in New Jersey refused, initially, to find a pharmaceutical patent invalid despite a U.S. Patent and Trademark Office finding of invalidity in an inter partes review (IPR) between the same parties.

Sanofi held that collateral estoppel which permits a ruling from one case to be applied in a separate casewas inappropriate where the standards of proof for invalidity were different (i.e., only a preponderance of evidence in the PTO, versus clear and convincing evidence in federal courts).

Ultimately, the Sanofi court did accept the invalidity determination, but only after the Federal Circuit Court of Appeals affirmed the PTOs decision. That appellate ruling, however, merely affirmed that the PTO had correctly found invalidity applying the lower standard.

In 2020, the Northern District of California, in Cisco Sys. v. Capella Photonics Inc., did apply collateral estoppel to find patent invalidity where the Federal Circuit had already affirmed an IPR invalidity finding. The Cisco court distinguished Sanofi as having occurred before appellate review of the IPRciting XY LLC v. Trans Ova Genetics, where the Federal Circuit held that collateral estoppel applies once the appeals court affirms the patent office on invalidity.

Interestingly, the XY case garnered a dissent from Circuit Judge Pauline Newman who pointed to the different standards in IPRs as a reason not to apply collateral estoppeleven after appellate affirmance of an IPR holding. Newman further noted that Supreme Court jurisprudence has repeatedly held that collateral estoppel is not to be automatically applied.

These decisions reveal tensions as to the collateral estoppel effect of IPR decisions in federal district court litigations.

Modern day collateral estoppel law derives from a landmark patent case. In Blonder-Tongue Laboratories Inc. v. University of Illinois Foundation, the Supreme Court held that a defendant in federal court may assert patent invalidity based on collateral estoppel if a different defendant invalidated the patent in an earlier federal court case.

Before Blonder-Tongue, patentees could in theory continue to assert a patent against different defendants after an invalidity rulingand thus a patent could be both effectively valid and invalid.

Nonetheless, as Judge Newman pointed out in her dissent in XY, the Blonder-Tongue case did not require automatic application of collateral estoppel but instead required the trial court to examine whether there were any reasons not to apply estoppele.g., if the issues being litigated in the two cases were not the same. And the Supreme Court has explained, in B&B Hardware Inc. v. Hargis Indus., that issues are not identical if the second action involves application of a different legal standard, even though the factual setting of both suits may be the same.

Citing B&B Hardware, Sanofi held that the different legal standards in IPRs preclude estoppel. The different standards have also led the Federal Circuit to hold, in Novartis AG v. Noven Pharms. Inc., that an IPR properly may reach a different conclusion [from a prior court ruling finding no invalidity] based on the same evidence.

These rulings seem discomforting. Our jurisprudence is premised upon treating like cases alike. How can a patent be both valid and invalid at the same time (even in the face of the same prior art)?

Indeed, the purpose of collateral estoppel is largely to avoid the anomaly of the same issue being adjudicated differently in different courts. Yet, are they really like cases if different standards are being applied? How can the patent office remove a property righta patentusing a lower standard of proof and then effectively impose that conclusion on an Article III court that has a higher standard of proof?

If and when these issues reach the Supreme Court they may provide a vehicle for refining the doctrine of collateral estoppel, as well as for considering whether the IPRs lower standard of proof for eliminating a property right is actually constitutionally permissiblean issue that the court has not specifically addressed when it has upheld IPRs in the face of other constitutional challenges.

For now, we live with the potential for Schrdingers patents"simultaneously valid and invalid during the time between IPR invalidation and appellate review. Like their quantum-physics feline counterparts, Schrdingers patents are curious creatures cloaked in uncertainty.

This column does not necessarily reflect the opinion of The Bureau of National Affairs, Inc. or its owners.

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Jason Lief is a co-founder of Lief Parke LLP in New York where he practices patent and IP litigation and counseling.

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Can a Patent Be Valid and Invalid at the Same Time? - Bloomberg Law

Credit: University of Twente

Light that is sent into a photonic crystal, cant go deeper than the so-called Bragg length. Deeper inside the crystal, light of a certain color range can simply not exist. Still, researchers of the University of Twente, the University of Iowa and the University of Copenhagen managed to break this law. They steer light into a crystal, using a programmed pattern, and demonstrate that it will reach places far beyond the Bragg length. They publish their findings in Physical Review Letters.

Photonic crystals have a regular pattern of nano pores etched in silicon. They are typically designed to work as a mirror for a certain color range of light. Inside the crystal, light of those colors is forbidden. Even if youd be able to place an atom inside the crystal, that typically emits one color, it will stop emitting light. The so-called Bragg length is the maximum distance light is allowed to travel, according to a well-known physics law.

This property can be used for creating perfect mirrors for certain wavelengths, but it also helps improving solar cells. Still, if there is a sign that says forbidden anywhere, then it is always tempting to go there. This is what the researchers did, they proved that light can penetrate the photonic crystal, much deeper than the Bragg length.

They managed to do this by using light that was pre-programmed, and by using the small imperfections that always come with creating nanostructures. These imperfections cause light waves to be scattered randomly inside the crystal. The researchers program the light in such a way that every location inside the photonic crystal can be reached. They even demonstrate a bright spot at five times the Bragg length, where light is enhanced100 times instead of decreased 100 to 1000 times.

This remarkable result can be used for creating stable quantum bits, for a light-driven quantum computer. The forbidden effect can also be employed in miniature on-chip light sources and lasers.

The research was done in theComplex Photonics group of Professor Willem Vos. The group is part of UTs MESA+ Institute. The first author, Ravitej Uppu, who worked in this group earlier on, is now a Professor at the University of Iowa. The research collaboration was continued, also together with the University of Copenhagen. It was supported by Dutch Research Council (NWO) programs Stirring of Light, Free form scattering optics and Self-assembled icosahedral quasicrystals with a band gap for visible light, by the Applied Nanophotonics section of the MESA+ Institute and the Center for Hybrid Quantum Networks of the Niels Bohr Institute in Copenhagen.

Reference: Spatially Shaping Waves to Penetrate Deep inside a Forbidden Gap by Ravitej Uppu, Manashee Adhikary, Cornelis A.M. Harteveld and Willem L. Vos, 27 April 2021, Physical Review Letters.DOI: 10.1103/PhysRevLett.126.177402

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Breaking the Laws of Physics: Steering Light to Places It Isnt Supposed to Go - SciTechDaily

The centerpiece of the Muon g-2 experiment at Fermilab is a 50-foot-diameter superconducting magnetic storage ring, which sits in its detector hall amidst electronics racks, the muon beamline and other equipment. Credit: Reidar Hahn, Fermilab

In 2001 at the Brookhaven National Laboratory in Upton, New York, a facility used for research in nuclear and high-energy physics, scientists experimenting with a subatomic particle called a muon encountered something unexpected.

To explain the fundamental physical forces at work in the universe and to predict the results of high-energy particle experiments like those conducted at Brookhaven, Fermilab in Illinois, and at CERNs Large Hadron Collider in Geneva, Switzerland, physicists rely on the decades-old theory called the Standard Model, which should explain the precise behavior of muons when they are fired through an intense magnetic field created in a superconducting magnetic storage ring. When the muon in the Brookhaven experiment reacted in a way that differed from their predictions, researchers realized they were on the brink of a discovery that could change sciences understanding of how the universe works.

Earlier this month, after a decades-long effort that involved building more powerful sensors and improving researchers capacity to process 120 terabytes of data (the equivalent of 16 million digital photographs every week), a team of scientists at Fermilab announced the first results of an experiment called Muon g-2 that suggests the Brookhaven find was no fluke and that science is on the brink of an unprecedented discovery.

UVA physics professor Dinko Poani has been involved in the Muon g-2 experiment for the better part of two decades, and UVA Today spoke with him to learn more about what it means.

Q. What are the findings of the Brookhaven and Fermilab Muon g-2 experiments, and why are they important?

A. So, in the Brookhaven experiment, they did several measurements with positiveand negative muons an unstable, more massive cousin of the electron under different circumstances, and whenthey averaged their measurements,they quantified a magnetic anomaly that is characteristic of the muon more precisely than ever before. According torelativistic quantum mechanics, the strength of the muons magnetic moment (a property it shares with a compass needle or a bar magnet) should be two in appropriate dimensionless units, the same as for an electron. The Standard Model states, however, that its not two, its a little bit bigger, and that difference is the magnetic anomaly. The anomaly reflects the coupling of the muon to pretty much all other particles that exist in nature. How is this possible?

The answer is that space itself is not empty; what we think of as a vacuum contains the possibility of the creation of elementary particles, given enough energy. In fact, these potential particles are impatient and are virtually excited, sparking in space for unimaginably short moments in time. And as fleeting as it is, this sparking is sensed by a muon, and it subtly affects the muons properties. Thus, the muon magnetic anomaly provides a sensitive probe of the subatomic contents of the vacuum.

To the enormous frustration of all the practicing physicists of my generation and younger, the Standard Model has been maddeningly impervious to challenges. We know there are things that must exist outside of it because it cannot describe everything that we know about the universe and its evolution. For example, it does not explain the prevalence of matter over antimatter in the universe, and it doesnt say anything about dark matter or many other things, so we know its incomplete. And weve tried very hard to understand what these things might be, but we havent found anything concrete yet.

So, with this experiment, were challenging the Standard Model with increasing levels of precision. If the Standard Model is correct, we should observe an effect that is completely consistent with the model because it includes all the possible particles that are thought to be present in nature, but if we see a different value for this magnetic anomaly, it signifies that theres actually something else. And thats what were looking for: this something else.

This experiment tells us that were on the verge of a discovery.

Q. What part have you been able to play in the experiment?

A. I became a member of this collaboration when we had just started planning for the follow-up to the Brookhaven experiment around 2005, just a couple of years after the Brookhaven experiment finished, and we were looking at the possibility of doing a more precise measurements at Brookhaven. Eventually that idea was abandoned, as it turned out that we could do a much better job at Fermilab, which had better beams, more intense muons and better conditions for experiment.

So, we proposed that around 2010, and it was approved and funded by U.S. and international funding agencies. An important part was funded by a National Science Foundation Major Research Instrumentation grant that was awarded to a consortium of four universities, and UVA was one of them. We were developing a portion of the instrumentation for the detection of positrons that emerge in decays of positive muons. We finished that work, and it was successful, so my group switched focus to the precise measurements of the magnetic field in the storage ring at Fermilab, a critical part of quantifying the muon magnetic anomaly. My UVA faculty colleague Stefan Baessler has also been working on this problem, and several UVA students and postdocs have been active on the project over the years.

Q. Fermilab has announced that these are just the first results of the experiment. What still needs to happen before well know what this discovery means?

A. It depends on how the results of our analysis of the yet-unanalyzed run segments turn out. The analysis of the first run took about three years. The run was completed in 2018, but I think now that we weve ironed out some of the issues in the analysis, it might go a bit faster. So, in about two years it would not be unreasonable to have the next result, which would be quite a bit more precise because it combines runs two and three. Then there will be another run, and we will probably finish taking data in another two years or so. The precise end of measurements is still somewhat uncertain, but I would say that about five years from now, maybe sooner, we should have a very clear picture.

Q. What kind of impact could these experiments have on our everyday lives?

A. One way is in pushing specific technologies to the extreme in solving different aspects of measurement to get the level of precision we need. The impact would likely come in fields like physics, industry and medicine. There will be technical spinoffs, or at least improvements in techniques, but which specific ones will come out of this, its difficult to predict. Usually, we push companies to make products that we need that they wouldnt otherwise make, and then a new field opens up for them in terms of applications for those products, and thats what often happens. The World Wide Web was invented, for example, because researchers like us needed to be able to exchange information in an efficient way across great distances, around the world, really, and thats how we have, well, web browsers, Zoom, Amazon and all these types of things today.

The other way we benefit is by educating young scientists some of whom will continue in the scientific and academic careers like myself but others will go on to different fields of endeavor in society. They will bring with them an expertise in very high-level techniques of measurement and analysis that arent normally found in many fields.

And then, finally, another outcome is intellectual betterment. One outcome of this work will be to help us better understand the universe we live in.

Q. Could we see more discoveries like this in the near future?

A. Yes, there is a whole class of experiments besides this one that look at highly precise tests of the Standard Model in a number of ways. Im always reminded of the old adage that if you lose your keys in the street late at night, you are first going to look for them under the street lamp, and thats what were doing. So everywhere theres a streetlight, were looking. This is one of those places and there are several others, well, I would say dozens of others, if you also include searches that are going on for subatomic particles like axions, dark matter candidates, exotic processes like double beta decay, and those kinds of things. One of these days, new things will be found.

We know that the Standard Model is incomplete. Its not wrong, insofar as it goes, but there are things outside of it that it does not incorporate, and we will find them.

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Are We on the Brink of a New Age of Scientific Discovery? - SciTechDaily

Our view of higher ed has been blinded by greed

Re Nicholas Tampios May 2 Ideas piece, How much money do English majors make? Dont ask.: Actually, glad you asked. Im doing fine, thanks, regardless of [my] major. Tampio ends his essay about the ill-conceived proposed College Transparency Act with a reference to what it would produce: a higher education system in the image of economists and businesspeople. But he never mentions greed.

We have strangled ourselves with greed. Instead of allowing 18-year-olds to develop their intellect, become curious, and build character by taking a range of courses and changing their minds while in the process of finding out who they might be we are continuing the diabolical process of producing limited, iPhone-distracted young adults with no perspective on the world.

Our higher-ed system has become embarrassing. So were going to talk college students out of studying history, literature, and philosophy because it wont put money in their pockets? We truly have become a nation of fools.

Laura Duffy

Newton

An English majors cautionary ode to practical-mindedness

Nicholas Tampio is correct in his opposition to the College Transparency Act, an unnecessary government solution to a problem that doesnt exist. If prospective college students want to know which majors pay the most (or the least), they can find that information on Google. Took me 10 seconds.

But Tampio is dead wrong in his assertion that students should follow their passions when choosing a college major. I guess if you want to have roommates for the rest of your life, a major in some obscure humanities field would be a good, passionate choice. But dont forget to buy soap on a rope; itll be convenient for the times you trundle back and forth to the bathroom that you share with other passionate degree holders.

Dave Rossow

Boylston

The writer is a recovering English major.

Family and its liberal arts majors have done quite well, thank you

Our three liberal arts major children (undergraduates in psychology-sociology, graphic design, and English-humanities) have all gone on to successful careers in business, entrepreneurship, and finance, as have I, another English major. English majors may not learn quantum physics, but they can do what a lot of STEM graduates cant do as effectively: read, write, and analyze. Dont sell the degree short.

Gail Schubert

Roslindale

Some may have the luxury to opine on the point of college

Nicholas Tampio, a professor of political science at Fordham University, reveals himself by saying hes worried about nudging students and families into viewing college as being primarily about making money. As a first-generation college student who relied on scholarships, loans, and work to attend a great university, I was lucky to have pieced it together to chart my path without even adequate career-counseling advice. This professor might need to sit in on some economics classes to understand that higher ed is, in fact, all about career opportunities for most scholars, not only to inform and motivate students to apply their own skills, but to rationalize the cost of the education itself, with a growing share subsidized by limited taxpayer and endowment resources. This does not exclude any students ability to learn, analyze, and appreciate life broadly.

Tom Pappas

Dartmouth

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Can you really put a price on your college major? - The Boston Globe