Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International

Wikipedia Affiliate Button

Home > Press > Generating high-quality single photons for quantum computing: New dual-cavity design emits more single photons that can carry quantum information at room temperature

MIT researchers have designed a new single-photon emitter that generates, at room temperature, more of the high-quality photons that could be useful for practical quantum computers, quantum communications, and other quantum devices.
MIT researchers have designed a new single-photon emitter that generates, at room temperature, more of the high-quality photons that could be useful for practical quantum computers, quantum communications, and other quantum devices.

Abstract:
MIT researchers have designed a way to generate, at room temperature, more single photons for carrying quantum information. The design, they say, holds promise for the development of practical quantum computers.

Generating high-quality single photons for quantum computing: New dual-cavity design emits more single photons that can carry quantum information at room temperature

Cambridge, MA | Posted on May 17th, 2019

Quantum emitters generate photons that can be detected one at a time. Consumer quantum computers and devices could potentially leverage certain properties of those photons as quantum bits ("qubits") to execute computations. While classical computers process and store information in bits of either 0s or 1s, qubits can be 0 and 1 simultaneously. That means quantum computers could potentially solve problems that are intractable for classical computers.

A key challenge, however, is producing single photons with identical quantum properties -- known as "indistinguishable" photons. To improve the indistinguishability, emitters funnel light through an optical cavity where the photons bounce back and forth, a process that helps match their properties to the cavity. Generally, the longer photons stay in the cavity, the more they match.

But there's also a tradeoff. In large cavities, quantum emitters generate photons spontaneously, resulting in only a small fraction of photons staying in the cavity, making the process inefficient. Smaller cavities extract higher percentages of photons, but the photons are lower quality, or "distinguishable."

In a paper published today in Physical Review Letters, the researchers split one cavity into two, each with a designated task. A smaller cavity handles the efficient extraction of photons, while an attached large cavity stores them a bit longer to boost indistinguishability.

Compared to a single cavity, the researchers' coupled cavity generated photons with around 95 percent indistinguishability, compared to 80 percent indistinguishability, with around three times higher efficiency.

"In short, two is better than one," says first author Hyeongrak "Chuck" Choi, a graduate student in the MIT Research Laboratory of Electronics (RLE). "What we found is that in this architecture, we can separate the roles of the two cavities: The first cavity merely focuses on collecting photons for high efficiency, while the second focuses on indistinguishability in a single channel. One cavity playing both roles can't meet both metrics, but two cavities achieves both simultaneously."

Joining Choi on the paper are: Dirk Englund, an associate professor of electrical engineering and computer science, a researcher in RLE, and head of the Quantum Photonics Laboratory; Di Zhu, a graduate student in RLE; and Yoseob Yoon, a graduate student in the Department of Chemistry.

The relatively new quantum emitters, known as "single-photon emitters," are created by defects in otherwise pure materials, such as diamonds, doped carbon nanotubes, or quantum dots. Light produced from these "artificial atoms" is captured by a tiny optical cavity in photonic crystal -- a nanostructure acting as a mirror. Some photons escape, but others bounce around the cavity, which forces the photons to have the same quantum properties -- mainly, various frequency properties. When they're measured to match, they exit the cavity through a waveguide.

But single-photon emitters also experience tons of environmental noise, such as lattice vibrations or electric charge fluctuation, that produce different wavelength or phase. Photons with different properties cannot be "interfered," such that their waves overlap, resulting in interference patterns. That interference pattern is basically what a quantum computer observes and measures to do computational tasks.

Photon indistinguishability is a measure of photons' potential to interfere. In that way, it's a valuable metric to simulate their usage for practical quantum computing. "Even before photon interference, with indistinguishability, we can specify the ability for the photons to interfere," Choi says. "If we know that ability, we can calculate what's going to happen if they are using it for quantum technologies, such as quantum computers, communications, or repeaters."

In the researchers' system, a small cavity sits attached to an emitter, which in their studies was an optical defect in a diamond, called a "silicon-vacancy center" -- a silicon atom replacing two carbon atoms in a diamond lattice. Light produced by the defect is collected into the first cavity. Because of its light-focusing structure, photons are extracted with very high rates. Then, the nanocavity channels the photons into a second, larger cavity. There, the photons bounce back and forth for a certain period of time. When they reach a high indistinguishability, the photons exit through a partial mirror formed by holes connecting the cavity to a waveguide.

Importantly, Choi says, neither cavity has to meet rigorous design requirements for efficiency or indistinguishability as traditional cavities, called the "quality factor (Q-factor)." The higher the Q-factor, the lower the energy loss in optical cavities. But cavities with high Q-factors are technologically challenging to make.

In the study, the researchers' coupled cavity produced higher quality photons than any possible single-cavity system. Even when its Q factor was roughly one-hundredth the quality of the single-cavity system, they could achieve the same indistinguishability with three times higher efficiency.

The cavities can be tuned to optimize for efficiency versus indistinguishability -- and to consider any constraints on the Q factor -- depending on the application. That's important, Choi adds, because today's emitters that operate at room temperature can vary greatly in quality and properties.

Next, the researchers are testing the ultimate theoretical limit of multiple cavities. One more cavity would still handle the initial extraction efficiently, but then would be linked to multiple cavities that photons for various sizes to achieve some optimal indistinguishability. But there will most likely be a limit, Choi says: "With two cavities, there is just one connection, so it can be efficient. But if there are multiple cavities, the multiple connections could make it inefficient. We're now studying the fundamental limit for cavities for use in quantum computing."

###

Written by Rob Matheson, MIT News Office

####

For more information, please click here

Contacts:
Abby Abazorius

617-253-2709

Copyright © Massachusetts Institute of Technology

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related Links

Paper: "Cascaded cavities boost the indistinguishability of imperfect quantum emitters":

Related News Press

News and information

uSEE breakthrough unlocks the nanoscale world on standard biology lab equipment August 16th, 2019

Optofluidic chip with nanopore 'smart gate' developed for single molecule analysis: Programmable device enables on-demand delivery of individual biomolecules with feedback-controlled gating for high-throughput analysis August 16th, 2019

ULVAC Launches Revolutionary PZT Piezoelectric Thin-film Process Technology and HVM Solution for MEMS Sensors/Actuators: Enabling Reliable, High-quality Film Production for Next Generation Devices August 16th, 2019

RIT to upgrade Semiconductor and Microsystems Fabrication Laboratory through $1 million state grant: Upgrades to clean room will enhance university’s research capabilities in photonics, quantum technologies and smart systems August 16th, 2019

Possible Futures

uSEE breakthrough unlocks the nanoscale world on standard biology lab equipment August 16th, 2019

ULVAC Launches Revolutionary PZT Piezoelectric Thin-film Process Technology and HVM Solution for MEMS Sensors/Actuators: Enabling Reliable, High-quality Film Production for Next Generation Devices August 16th, 2019

RIT to upgrade Semiconductor and Microsystems Fabrication Laboratory through $1 million state grant: Upgrades to clean room will enhance university’s research capabilities in photonics, quantum technologies and smart systems August 16th, 2019

Probing the Origin of Alzheimer’s . . . with Transistors: Novel high-sensitivity detector could aid in early diagnosis August 15th, 2019

Chip Technology

ULVAC Launches Revolutionary PZT Piezoelectric Thin-film Process Technology and HVM Solution for MEMS Sensors/Actuators: Enabling Reliable, High-quality Film Production for Next Generation Devices August 16th, 2019

Toppan Photomasks and GLOBALFOUNDRIES Enter into Multi-Year Supply Agreement August 15th, 2019

Sharp meets flat in tunable 2D material: Rice's new atom-flat compounds show promise for optoelectronics, advanced computing August 12th, 2019

New synthesis method opens up possibilities for organic electronics August 7th, 2019

Nanotubes/Buckyballs/Fullerenes/Nanorods

Damaged hearts rewired with nanotube fibers: Texas Heart doctors confirm Rice-made, conductive carbon threads are electrical bridges August 14th, 2019

Rice lab produces simple fluorescent surfactants: Compounds show promise for use in medicine, manufacturing August 5th, 2019

Oddball edge wins nanotube faceoff: Rice U. theory shows peculiar 'Janus' interface a common mechanism in carbon nanotube growth July 29th, 2019

Skoltech scientists developed a novel method to fine-tune the properties of carbon nanotubes July 24th, 2019

Quantum Computing

RIT to upgrade Semiconductor and Microsystems Fabrication Laboratory through $1 million state grant: Upgrades to clean room will enhance university’s research capabilities in photonics, quantum technologies and smart systems August 16th, 2019

Sharp meets flat in tunable 2D material: Rice's new atom-flat compounds show promise for optoelectronics, advanced computing August 12th, 2019

RIT awarded NSF funding to conceptualize Quantum Photonic Institute: RIT will develop plan for open-access Quantum Foundry for quantum photonic circuits August 7th, 2019

Virginia Tech researchers lead breakthrough in quantum computing July 26th, 2019

Discoveries

uSEE breakthrough unlocks the nanoscale world on standard biology lab equipment August 16th, 2019

Optofluidic chip with nanopore 'smart gate' developed for single molecule analysis: Programmable device enables on-demand delivery of individual biomolecules with feedback-controlled gating for high-throughput analysis August 16th, 2019

Probing the Origin of Alzheimer’s . . . with Transistors: Novel high-sensitivity detector could aid in early diagnosis August 15th, 2019

Damaged hearts rewired with nanotube fibers: Texas Heart doctors confirm Rice-made, conductive carbon threads are electrical bridges August 14th, 2019

Announcements

uSEE breakthrough unlocks the nanoscale world on standard biology lab equipment August 16th, 2019

Optofluidic chip with nanopore 'smart gate' developed for single molecule analysis: Programmable device enables on-demand delivery of individual biomolecules with feedback-controlled gating for high-throughput analysis August 16th, 2019

ULVAC Launches Revolutionary PZT Piezoelectric Thin-film Process Technology and HVM Solution for MEMS Sensors/Actuators: Enabling Reliable, High-quality Film Production for Next Generation Devices August 16th, 2019

RIT to upgrade Semiconductor and Microsystems Fabrication Laboratory through $1 million state grant: Upgrades to clean room will enhance university’s research capabilities in photonics, quantum technologies and smart systems August 16th, 2019

Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers

uSEE breakthrough unlocks the nanoscale world on standard biology lab equipment August 16th, 2019

Optofluidic chip with nanopore 'smart gate' developed for single molecule analysis: Programmable device enables on-demand delivery of individual biomolecules with feedback-controlled gating for high-throughput analysis August 16th, 2019

Probing the Origin of Alzheimer’s . . . with Transistors: Novel high-sensitivity detector could aid in early diagnosis August 15th, 2019

Damaged hearts rewired with nanotube fibers: Texas Heart doctors confirm Rice-made, conductive carbon threads are electrical bridges August 14th, 2019

Quantum nanoscience

A graphene superconductor that plays more than one tune: Researchers at Berkeley Lab have developed a tiny toolkit for scientists to study exotic quantum physics July 19th, 2019

Dresden physicists use nanostructures to free photons for highly efficient white OLEDs: Trapped light particles July 12th, 2019

Research Reveals Exotic Quantum States in Double-Layer Graphene: Findings shed new light on the nature of electron interactions in quantum systems and establish a potential new platform for future quantum computers June 26th, 2019

Mysterious Majorana quasiparticle is now closer to being controlled for quantum computing: Princeton researchers detect a robust Majorana quasiparticle and show how it can be turned on and off June 14th, 2019

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project