Researchers generate high-quality quantum light with modular waveguide
device
New approach could enable faster and more practical optical quantum
computers

Date:
April 12, 2022
Source:
Optica
Summary:
Researchers have successfully generated strongly nonclassical
light using a modular waveguide-based light source. By combining
a waveguide optical parametric amplifier (OPA) module created for
quantum experiments and a specially designed photon detector,
researchers were able to produce light in a superposition of
coherent states. The achievement represents a crucial step toward
creating faster and more practical optical quantum computers.



FULL STORY ==========================================================================
For the first time, researchers have successfully generated strongly nonclassical light using a modular waveguide-based light source. The achievement represents a crucial step toward creating faster and more
practical optical quantum computers.


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"Our goal is to dramatically improve information processing by developing faster quantum computers that can perform any type of computation
without errors," said research team member Kan Takase from the University
of Tokyo.

"Although there are several ways to create a quantum computer, light-based approaches are promising because the information processor can operate at
room temperature and the computing scale can be easily expanded." In the Optica Publishing Group journal Optics Express, a multi-institutional
team of researchers from Japan describe the waveguide optical parametric amplifier (OPA) module they created for quantum experiments. Combining
this device with a specially designed photon detector allowed them
to generate a state of light known as Schro"dinger cat, which is a superposition of coherent states.

"Our method for generating quantum light can be used to increase the
computing power of quantum computers and to make the information
processer more compact," said Takase. "Our approach outperforms
conventional methods, and the modular waveguide OPA is easy to operate
and integrate into quantum computers." Generating strongly nonclassical
light Continuous wave squeezed light is used to generate the various
quantum states necessary to perform quantum computing. For the best
computing performance, the squeezed light source must exhibit very low
levels of light loss and be broadband, meaning it includes a wide range
of frequencies.



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"We want to increase the clock frequency of optical quantum
computers, which can, in principle, achieve Terahertz frequencies,"
said Takase. "Higher clock frequencies enable faster execution of
computational tasks and allow the delay lines in the optical circuits to
be shortened. This makes optical quantum computers more compact while
also making it easier to develop and stabilize the overall system."
OPAs use nonlinear optical crystals to generate squeezed light, but conventional OPAs don't generate the quantum light with the properties necessary for faster quantum computing. To overcome this challenge,
researchers from the University of Tokyo and NTT Corporation developed
an OPA based on a waveguide-type device that achieves high efficiency
by confining light to a narrow crystal.

By carefully designing the waveguide and manufacturing it with precision processing, they were able to create an OPA device with much smaller propagation loss than conventional devices. It can also be modularized
for use in various experiments with quantum technologies. Designing the
right detector The OPA device was designed to create squeezed light at telecommunications wavelengths, a wavelength region that tends to exhibit
low losses. To complete the system, researchers needed a high-performance photon detector that worked at telecom wavelengths. However, standard
photon detectors based on semiconductors don't meet the performance requirements for this application.

Thus, researchers from University of Tokyo and National Institute of Information and Communications Technology (NICT) developed a detector
designed specifically for quantum optics. The new superconducting
nanostrip photon detector (SNSPD) uses superconductivity technology to
detect photons.

"We combined our new waveguide OPA with this photon detector to
generate a highly non-classical -- or quantum -- state of light called Schro"dinger cat," said Takase. "Generating this state, which is difficult
with conventional, low- efficiency waveguide OPAs, confirms the high performance of our waveguide OPA and opens the possibility of using this
device for a wide range of quantum experiments." The researchers are
now looking at how to combine high-speed measurement techniques with
the new waveguide OPA to get closer to their goal of ultrafast optical
quantum computing.


========================================================================== Story Source: Materials provided by Optica. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Kan Takase, Akito Kawasaki, Byung Kyu Jeong, Mamoru Endo, Takahiro
Kashiwazaki, Takushi Kazama, Koji Enbutsu, Kei Watanabe,
Takeshi Umeki, Shigehito Miki, Hirotaka Terai, Masahiro Yabuno,
Fumihiro China, Warit Asavanant, Jun-ichi Yoshikawa, Akira
Furusawa. Generation of Schro"dinger cat states with Wigner
negativity using a continuous-wave low-loss waveguide optical
parametric amplifier. Optics Express, 2022; 30 (9): 14161 DOI:
10.1364/OE.454123 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220412161603.htm

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