Nav: Home

Control of quantum state of optical phonon in diamond induced by ultrashort light pulses

June 25, 2018

Ultrashort Light-pulse-induced vibrations of atoms in a lattice, called optical coherent phonons, have been controlled in various materials. However, different experiments demonstrating such control have been explained differently through empirical theories, and a unified theory based on quantum mechanics is lacking. Scientists at Tokyo Institute of Technology successfully formulated a unified theory for this phenomenon and experimentally verified it in diamond, the optical phonons of which have great potential for application in quantum information technology.

When extremely short optical pulse enters a solid, the atoms in its lattice start vibrating. Collectively, such vibrations of atoms exhibit both wave-like and particle-like behavior, and in quantum mechanics, these vibrations are called coherent optical phonons because they are induced by light and oscillate in phase. Phonons can determine various physical properties of solids, such as thermal and electrical conductivities. In previous experiments, the properties of coherent optical phonons, such as amplitude and phase, have been successfully controlled in various materials through a technique called coherent control, which has been made possible by advances in ultrafast laser technology. However, the results of different coherent control experiments have been explained using different empirical theories. Therefore, a unified quantum mechanical theory that explains the control of optical phonons is required.

Research team led by Professor Kazutaka G. Nakamura at Tokyo Institute of Technology (Tokyo Tech) collaborated with Professor Yutaka Shikano at Quantum Computing Center, Keio University and Institute for Quantum Studies, Chapman University recently formulated a theoretical framework that fundamentally and practically explains the generation and detection of coherent optical photons. The theory is based on a model involving two states of electrons as well as the quantum harmonic oscillator, one of the few quantummechanical systems for which an exact solution is known. Calculations based on this theory showed that the amplitude of a controlled phonon can be expressed by the sum of two sinusoidal functions.

To test this theory, the scientists conducted an experiment of coherent control in diamond. Diamond is a very important material in this field because the coherent control of its optical phonons is promising to develop quantum memory In the experiment, coherent control is achieved by employing two extremely short laser pulses, known as pump pulses: one pulse induces an oscillation, or phonons, while the other controls the amplitude of oscillation. The time gap between the two pulses is varied to control the properties of the generated phonons. A probe pulse sent with a delay after the two pump pulses is used to measure the properties of the generated phonons by detecting changes in the transmitted intensity of this pulse with respect to the delay.

The measured amplitude and phase of controlled oscillations induced by the pump pulses in diamond showed a remarkable agreement with the predictions of the theory. Thus, a comprehensive understanding of the coherent control of coherent optical phonons has been achieved. This theory is expected to be useful in the development of memory systems for quantum computing, in addition to other applications in electronics, optics, materials science, and superconductivity.
-end-


Tokyo Institute of Technology

Related Quantum Computing Articles:

New method could enable more stable and scalable quantum computing, Penn physicists report
Researchers from the University of Pennsylvania, in collaboration with Johns Hopkins University and Goucher College, have discovered a new topological material which may enable fault-tolerant quantum computing.
Stanford team brings quantum computing closer to reality with new materials
Quantum computing could outsmart current computing for complex problem solving, but only if scientists figure out how to make it practical.
Computing -- quantum deep
In a first for deep learning, an Oak Ridge National Laboratory-led team is bringing together quantum, high-performance and neuromorphic computing architectures to address complex issues that, if resolved, could clear the way for more flexible, efficient technologies in intelligent computing.
Legacy of brilliant young scientist is a major leap in quantum computing
Researchers from the University of Bristol and Université Libre de Bruxelles have theoretically shown how to write programs for random circuitry in quantum computers.
WSU mathematician breaks down how to defend against quantum computing attacks
WSU mathematician Nathan Hamlin is the author of a new paper that explains how a code he wrote for a doctoral thesis, the Generalized Knapsack Code, could thwart hackers armed with next generation quantum computers.
More Quantum Computing News and Quantum Computing Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#534 Bacteria are Coming for Your OJ
What makes breakfast, breakfast? Well, according to every movie and TV show we've ever seen, a big glass of orange juice is basically required. But our morning grapefruit might be in danger. Why? Citrus greening, a bacteria carried by a bug, has infected 90% of the citrus groves in Florida. It's coming for your OJ. We'll talk with University of Maryland plant virologist Anne Simon about ways to stop the citrus killer, and with science writer and journalist Maryn McKenna about why throwing antibiotics at the problem is probably not the solution. Related links: A Review of the Citrus Greening...