System Bits: March 5

The new electronics field of magnonics
Transistors keep shrinking to dimensions that are difficult to fabricate. There is doubt in the semiconductor industry about the possibility of producing 1-nanometer features with existing process technology. The answer may lie in magnonic currents: quasi-particles associated with waves of magnetization, or spin waves, in magnetic materials.

Researchers at the University of California, Riverside, studied the level of noise associated with the propagation of magnon current, which could lead to harnessing magnonic technology for next-generation devices.

Alexander Balandin, a distinguished professor of electrical and computer engineering in UC Riverside’s Marlan and Rosemary Bourns College of Engineering, led a team that created a microchip that generated a magnonic current between transmitting and receiving antennae.

Magnons don’t produce much noise at low-power levels, but high-power levels resulted in unusual noise that the researchers dubbed random telegraph signal noise, fluctuations that differ from the typical noise of electrons.

“Magnonic devices should be preferably operating with low-power levels,” Balandin said. “One can say that the noise of magnons is discreet at low power but becomes high and discrete at a certain threshold of power. This constitutes the discreet charm of the magnonic devices. Our results also tell us possible strategies for keeping the noise level low.”

When it comes to power requirements in electronics, the lower, the better, these days.

Reducing quantum error in logic gates
Scientists at Australia’s University of Sydney helped to improve quantum computer technology, using codes that can detect and discard errors in the logic gates of those machines. Working with one of IBM’s Q series quantum computers, Dr. Robin Harper and Professor Steven Flammia tested the error detection codes.

“This is really the first time that the promised benefit for quantum logic gates from theory has been realized in an actual quantum machine,” said Dr. Harper, lead author of a new paper just published in the Physical Review Letters journal.

Dr. Jay Gambetta, IBM Fellow and principal theoretical scientist with IBM Q, said, “This paper is a great example of how scientists can use our publicly available cloud systems to probe fundamental problems. Here Harper and Flammia show that ideas of fault tolerance can be explored on real devices we are building and already deploying, today.”

Gambetta and IBM Q’s Sarah Sheldon blogged about the new IBM Q System One, a quantum computing system for commercial use.

“Current devices tend to be too small, with limited interconnectivity between qubits and are too ‘noisy’ to allow meaningful computations,” Dr. Harper said. “However, they are sufficient to act as test beds for proof of principle concepts, such as detecting and potentially correcting errors using quantum codes.”

Professor Flammia said, “One way to look at this is through the concept of entropy. All systems tend to disorder. In conventional computers, systems are refreshed easily and reset using DRAM and other methods, effectively dumping the entropy out of the system, allowing ordered computation.

“In quantum systems, effective reset methods to combat entropy are much harder to engineer. The codes we use are one way to dump this entropy from the system.”

Image credit: Artist’s rendering, University of Waterloo

New quantum sensor may advance cancer treatment
Researchers at the University of Waterloo’s Institute of Quantum Computing have come up with a quantum sensor that promises to provide significant advancements in long-range 3D imaging and monitoring the success of cancer treatments.

“A sensor needs to be very efficient at detecting light. In applications like quantum radar, surveillance, and nighttime operation, very few particles of light return to the device,” said principal investigator Michael Reimer, an IQC faculty member and assistant professor in the Faculty of Engineering’s electrical and computer engineering department. “In these cases, you want to be able to detect every single photon coming in.”

The next-generation quantum sensor designed in Reimer’s lab at the Canadian university is so fast and efficient that it can absorb and detect a single particle of light, a photon, and refresh for the next one within nanoseconds. The researchers created an array of tapered nanowires that turn incoming photons into electric current that can be amplified and detected.

Remote sensing, high-speed imaging from space, acquiring long-range high-resolution 3D images, quantum communication, and singlet oxygen detection for dose monitoring in cancer treatment are all applications that could benefit from the kind of robust single-photon detection that this new quantum sensor provides, the university says.

“This device uses indium phosphide nanowires. Changing the material to indium gallium arsenide, for example, can extend the bandwidth even further towards telecommunications wavelengths while maintaining performance,” Reimer said. “It’s state-of-the art now, with the potential for further enhancements.”