Improving Quantum Cryptography with Twisted Light

Category: Science & Technology Posted: March 23, 2015 06:33AM Author: Guest_Jim_*

Securing communications is of great importance to many, so a system that is protected from intrusion by the laws of physics is highly desirable. Quantum cryptography is such a system and many are working on various ways to improve the methods of using it. Researchers at the University of Rochester have recently found that using twisted light can improve security even more.

So-called twisted light uses orbital angular momentum (OAM) to encode information, instead of polarization, a more common option. The researchers were able to show that by using OAM and angular position they could encode a seven dimensional, or letter alphabet with the photons. This alphabet is important for quantum key distribution (QKD), which is the start of quantum cryptography. To use QKD the users will encode the key with this alphabet onto the photons. Only if both the sender and receiver are measuring along the same dimension will they get the same key, and by comparing what was original sent and received, both parties can determine the key without publicly transmitting what it is. An eavesdropper would disrupt the transmission in a detectable way, thereby allowing the users to avoid interception.

Thus far the researchers have demonstrated their system working at 4 kHz with 93% accuracy, so the researchers still have some work to do before reaching the long term goal of a GHz rate. Besides the quantum cryptography applications, this new system also allows for each photon to carry 2.05 bits of information, but with more sophisticated equipment, the photons could hold 4.17 bits, and allow for an even more secure 25 letter alphabet.

Source: University of Rochester

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Improving Quantum Cryptography with Twisted Light