For the first time, researchers have succeeded in powerfully generating non-classical light using a standard waveguide-based light source. The achievement represents a critical step towards creating faster and more practical optical computers.
“Our goal is to dramatically improve information processing by developing faster quantum computers that can perform any kind of computation without errors,” said research team member Kan Takas from the University of Tokyo. “Although there are several ways to create a quantum computer, light-based methods are promising because the information processor can operate at room temperature and computing can be easily scaled up.”
In Optica Publishing Group Optix Express, a multi-institutional team of researchers from Japan has described the waveguide optical amplifier (OPA) module they created for quantum experiments. The combination of this device and a specially designed photon detector allowed them to generate a state of light known as Schrödinger’s cat, a superposition of coherent states.
“Our quantum light generation method can be used to increase the computing power of quantum computers and to make the information processor more compact,” Takase said. “Our approach is superior to conventional methods, and the standard OPA waveguide is easy to operate and integrate into quantum computers.”
Powerfully generating non-classical light
Continuous wave compressed light is used to generate the different quantum states needed to perform quantum computing. For best computing performance, a compressed light source must exhibit very low levels of light loss and be a broad band, meaning that it includes a wide range of frequencies.
“We want to increase the clock frequency of optical quantum computers, which can, in principle, achieve terahertz frequencies,” Takase said. “Higher clock frequencies enable faster execution of computational tasks and allow the delay lines in optical circuits to be shortened. This makes optical quantum computers more compact while also facilitating the development and stability of the entire system.”
OPA uses nonlinear photonic crystals to generate compressed light, but conventional OPA does not generate quantum light with the properties needed 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 fabricating it with precise processing, they were able to create an OPA device with much lower propagation loss than conventional devices. It can also be modular for use in various experiments with quantum technologies.
Correct Detector Design
The OPA device is designed to create compressed light at telecom wavelengths, a wavelength region that tends to show low losses. To complete the system, the researchers needed a high-performance photon detector operating at communications wavelengths. However, standard semiconductor-based photon detectors do not meet the performance requirements for this application.
Thus, researchers from the University of Tokyo and the National Institute of Information and Communication Technologies (NICT) have developed a detector specifically designed for quantum optics. A new superconducting nanoribbon photon detector (SNSPD) uses superconductivity technology to detect photons.
“We combined the new OPA waveguide with this photon detector to generate a non-classical state – or quantum – of light called Schrödinger’s cat,” Takase said. “Establishing this state, which is difficult with OPA for a conventional low-efficiency waveguide, confirms the high performance of our OPA waveguide 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 OPA waveguide to get closer to their goal of ultrafast optical quantum computing.
Designed Single Photons: Optical Control of Photons as Key to New Technologies
Kan Takase et al, Cases of Schrödinger’s generation with Wigner negativity using a low-wavelength waveguide optical preamplifier, Optix Express (2022). doi: 10.1364/OE.454123
the quote: Researchers produce high-quality quantum light using a modular waveguide device (2022, April 12) Retrieved on April 13, 2022 from https://phys.org/news/2022-04-high-quality-quantum-modular-waveguide-device .html
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