Team Generates 10.1±0.2-dB Squeezed Light Via Broadband Waveguide Optical Parametric Amplifier with Improved Phase Locking

Generating squeezed light, a crucial resource for advancing quantum technologies, recently achieved a significant leap forward thanks to work led by Kazuki Hirota and Takahiro Kashiwazaki from The University of Tokyo and NTT, Inc., along with Gyeongmin Ha, Taichi Yamashima, Pawaphat Jaturaphagorn, and Takumi Suzuki. The team demonstrates the generation of 10. 1 decibel squeezed light using a broadband waveguide optical parametric amplifier, surpassing previous results and paving the way for more robust quantum systems. This achievement stems from a novel phase-locking method that minimises signal loss and reduces phase fluctuations, overcoming a key challenge in squeezing technology. By breaking the conventional trade-off between signal acquisition and squeezing degradation, the researchers have significantly improved both the stability and efficiency of squeezed light generation, bringing fault-tolerant quantum computation closer to reality.

This work addresses the challenge of achieving high levels of quantum noise reduction over a broad bandwidth, and successfully generated squeezed light exceeding 8 decibels, a significant achievement in reducing quantum noise. The system utilizes a modular design, allowing for easy scaling to process more quantum information, and operates over a broad bandwidth essential for efficient quantum information encoding and processing. The core of the system is a waveguide optical parametric amplifier, preferred for its efficiency and ability to operate at high bandwidths, fabricated using a periodically poled lithium niobate waveguide that enables efficient nonlinear optical interactions.

An all-optical feedforward technique further enhances the system’s performance and stability. This technology supports the development of analog optical quantum computers, offering a different approach to quantum computation, and has potential applications in quantum cryptography, quantum sensing, and quantum simulation. This research contributes to the advancement of practical and scalable quantum computers based on continuous variables, bringing the field closer to realizing fault tolerance. It is part of a larger effort to build a full-stack analog optical quantum computer with a hundred inputs, potentially revolutionizing quantum information processing.

Broadband Squeezed Light with Improved Phase Detection

Scientists have generated 10. 1 decibel-level squeezed light using a broadband periodically poled lithium niobate waveguide optical parametric amplifier, building upon previous work. This advancement addresses limitations in phase fluctuations and optical losses within the measurement system, significantly improving performance. The team pioneered a novel phase detection technique that eliminates the need to tap a portion of the squeezed light to obtain a phase-locking signal, a common practice that typically degrades the squeezing level. This innovative technique involves a phase-detection optical parametric amplifier seeded by light positioned before the squeezer, effectively circumventing the trade-off between generating a high-signal-to-noise ratio phase-locking signal and maintaining high squeezing levels.

Consequently, phase fluctuations were reduced to 9 milliradians, and total optical loss decreased to 8 percent, demonstrating substantial improvements in system stability and efficiency. The strong nonlinear effects achievable within the PPLN waveguides enable single-pass optical parametric amplification and terahertz-order squeezing bandwidth. By optimizing the phase detection method and minimizing optical losses, scientists achieved a breakthrough in broadband squeezed light generation, exceeding the minimum noise level required for fault-tolerant quantum computation using approximate Gottesman-Kitaev-Preskill coding. This advancement represents a significant step towards realizing practical, high-performance quantum technologies.
<h310. 1 >Decibel Squeezing Achieved with Waveguide Amplifier

Scientists have achieved a squeezing level of 10. 1 decibels using a broadband periodically poled lithium niobate waveguide parametric amplifier, representing a significant step towards realizing fault-tolerant quantum technologies. This breakthrough builds upon previous work, and was accomplished through reductions in both phase fluctuations and overall system losses. The team developed a novel phase detection technique that avoids tapping the squeezed light itself, thereby eliminating a fundamental trade-off between phase-locking precision and signal degradation. Experiments revealed a reduction in phase fluctuation angle to 9 milliradians, and a decrease in total optical losses to 8 percent.

This improvement was achieved by extracting a portion of the probe and pump light before the squeezing process and directing it into a separate phase-detection optical parametric amplifier. By performing phase locking on this pre-squeezed light, the team circumvented the need to tap the squeezed output, preserving its integrity and maximizing the squeezing level. The innovative method allows for independent adjustment of the probe and pump power in the phase-detection amplifier, generating a strong error signal with a high signal-to-noise ratio.

High-Fidelity Squeezed Light Generation Demonstrated

Scientists have achieved the generation of 10. 1 decibel-level squeezed light using a broadband periodically poled lithium niobate waveguide parametric amplifier. This advancement builds upon previous work, and represents a significant reduction in both phase fluctuations and overall optical losses within the measurement system. The team implemented a novel phase detection technique that avoids the typical trade-off between obtaining a strong phase-locking signal and maintaining the integrity of the squeezed light. This improvement was achieved by employing a phase-detection optical parametric amplifier seeded with light before the main squeezing process, enabling precise phase locking without compromising the squeezed state.

As a result, phase fluctuations were reduced to 9 milliradians and total optical loss to 8 percent. Achieving this level of squeezing relaxes the requirements for generating specific quantum states, and is a crucial step towards realizing practical, fault-tolerant, and ultra-fast optical quantum computation. Furthermore, this research contributes to the development of emerging analog quantum computing platforms with potential applications in artificial intelligence, particularly in the creation of optical neural networks.