Researchers at the University of California, Santa Barbara recently addressed a major issue in security by successfully transferring reliable and ultra-secure communication via quantum-encrypted information.

Developments surrounding a new breed of silicon-based supercomputers, though still in their infancy, may mark a shift on the limitations of modern digital technology.

According to Amit Vainsencher, a physics graduate student and co-author of the paper, the application of their technology has the potential to increase privacy.

“You can use it to communicate with people over fiber optics using quantum states, so if someone was spying on you by splicing the fiber and peeking into it, that would change the state and you would know someone was leaking into your communications,” Vainsencher said.

In conventional computing, information is represented as a binary code of zeroes and ones called bits, expressed by a flickering set of transistors being turned either on or off. In quantum mechanics, however, properties of superposition permit aberrations such as an electron simultaneously exhibiting two opposite spins or a single particle existing in two different places in a given instant. These anomalies allowed for the design of a quantum bit or “qubit” which can express a zero and one at the same time in the binary code.

This, in addition to another feature of quantum mechanics called entanglement, whereby the state (e.g. spin, direction, polarization or location) of one particle determines that state of another, allows for quantum machines to run multiple calculations in parallel , explaining their extraordinary speed. A computer containing 300 qubits can perform more calculations at an instant than there are atoms in the universe.

Co-author Andrew Cleland, associate director of the California Nanosystems Institute and physics professor, said that current commercial systems, though they already use the principle of superposition and entanglement, are slow and inefficient.

“They encode information in light, they send it down a fiber optic and the person receiving it is the only one that can interpret [or] decode that information. The problem is that the commercial systems you can get are really slow, so you cannot send a lot of information using them. And that is because the way they generate this encrypted information is too slow,” Cleland said. “We think it may be possible to do it a thousand or 10,000 times faster than today’s commercial systems.”

The paper defines a concept for nanomechanical transducer, which was shown to demonstrate a unitary transfer of microwave signals to optical photons. The prototype device features an optomechanical crystal plated with a piezoelectric material in a way that makes it compatible with superconducting qubits.

“When we build our superconducting circuits, those things operate on a cryogenic system nearly at absolute zero so that the thermal noise is really small compared with the quantum of energy associated with microwave signals. So we are building a transducer that can take a microwave signal and turn it into an optical signal that can survive at room temperature,” said Cleland.

Operating the transducer over the single phonon limit, the team was able to generate strong coherent interactions between the electrical, mechanical and optical modes in the piezoelectric optomechanical crystal using classical signals.

“We only tested the device at room temperature, and it has to work cold if we are actually going to get it to work quantum mechanically” said Cleland.

The next undertaking will likely demonstrate similar operational behavior of the transducer in a colder temperature, this time using quantum states. By transferring electrical signals into light, the team’s research may stand to dramatically increase the speed and protection of information.

 IMAGE COURTESY OF UCSB

 A version of this article appeared on page 5 of Tuesday October 15th’s print edition of the Daily Nexus.