Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

npj Quantum Information

Digital reconstruction of squeezed light for quantum information processing

Huy Quang Nguyen, Ivan D. Derkach, Adnan A. E. Hajomer, Hou-Man Chin, Akash nag Oruganti, Ulrik L. Andersen, Vladyslav C. Usenko, Tobias Gehring

Published May 3, 2025• 11 citations
Publisher

Abstract

Squeezed light plays a vital role in quantum information processing. However, its highly sensitive nature presents significant practical challenges, particularly in remote detection, which traditionally requires complex systems such as active phase locking, clock synchronization, and polarization control. Here, we propose and demonstrate an asynchronous detection method for squeezed light eliminating the need for these complex systems. By employing radio-frequency heterodyne detection with a locally generated local oscillator and applying a series of digital unitary transformations, we successfully reconstruct squeezed states of light. We validate our approach in two key applications: the distribution of squeezed light over a 10 km fiber channel, and passive continuous-variables quantum key distribution based on squeezed vacuum states between two labs connected via deployed fiber. This demonstrates a practical digital reconstruction method for squeezed light, opening new avenues for practical distributed quantum sensing networks and high-performance, long-distance quantum communication using squeezed states.

DOI
10.1038/s41534-025-01018-9

Related papers

Digital reconstruction of squeezed light for quantum information processing

Huy Quang Nguyen, Ivan D. Derkach, Adnan A. E. Hajomer +5 more

Squeezed light plays a vital role in quantum information processing. By nature, it is highly sensitive, which presents significant practical challenges, particularly in remote detection, traditionally requiring complex systems such as active phase locking, clock synchronization, and polarization control. Here, we propose and demonstrate an asynchronous detection method for squeezed light that eliminates the need for these complex systems. By employing radio-frequency heterodyne detection with a locally generated local oscillator and applying a series of digital unitary transformations, we successfully reconstruct squeezed states of light. We validate the feasibility of our approach in two key applications: the distribution of squeezed light over a 10 km fiber channel, and secure quantum key distribution between two labs connected via deployed fiber based on continuous variables using squeezed vacuum states without active modulation. This demonstrates a practical digital reconstruction method for squeezed light, opening new avenues for practical distributed quantum sensing networks and high-performance and long-distance quantum communication using squeezed states and standard telecom technology.

arXiv:2411.07666•Nov 12, 2024•1 citation

Transmission and Detection of Squeezed States of Light through an Optical Fiber with a Real-time True Local Oscillator

Iyad Suleiman, Jens Arnbak, Xueshi Guo +3 more

Transmission and accurate detection of squeezed states of light will play a central role in the future quantum internet, where quantum cryptography, communication and computation will coexist in an organic system. Their coherent detection has recently proven to be crucial for photonics-based quantum computing [1] , and to provide improvements in continuous variables quantum key distribution [2] [6] and quantum sensing [3] . Often when measuring a quantum state through coherent detection, the local oscillator field is transmitted along with the signal; however, in realistic long-distance optical fiber transmissions, where the needed local oscillator optical power increases exponentially with the distance, the system’s performance deteriorates due to nonlinear Brillouin scattering, and wavelength multiplexing schemes may be needed to avoid the issue. Moreover, transmitting a local oscillator opens security loopholes in quantum key distribution systems, where an eavesdropper can defy the security assessment from the trusted parties by gaining control over the local oscillator [4] . It is therefore very important to design coherent detection schemes that make use of independent local oscillators. We demonstrate the transmission single-mode squeezed light at 1550 nm wavelength through single-mode optical fibers (10 m and 10 km lengths) and its homodyne detection, using an independent local oscillator and a real-time phase-control system. Fig. 1a depicts the implemented physical setup: 1550 nm squeezed light is generated through spontaneous parametric downconversion [5] , couples into a single-mode optical fiber and propagates towards the homodyne detector for quadrature measurement. Real-time phase control consists in detecting the interference between a 40 MHz single-sideband pilot mode -phase-locked to the downconverted pump- and the local oscillator, estimating their instantaneous phase difference and implementing a fast and broad FPGA-based phase control on the local oscillator. As shown in Fig. 1b and 1c, with the presented scheme it was possible to steadily measure up to 3.6 dB of squeezing after a 10 m optical fiber transmission, and up to 1.5 dB of squeezing after a 10 km fiber transmission, with similar performance in terms of phase error and control stability. The presented system is simple, robust and cost-effective, and it will represent a standard class of techniques to detect not only squeezed states of light, but any arbitrary quantum state of light, including Schrödinger cat states, highly useful in quantum computation and error correction.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 21, 2021•2 citations

Practical continuous-variable quantum key distribution with squeezed light

Huy Quang Nguyen, Ivan D. Derkach, Hou-Man Chin +6 more

Continuous-variable quantum key distribution (CV-QKD) has gathered significant interest for its potential to achieve high secret key rates and seamless integration with existing optical communication infrastructure. State-of-the-art CV-QKD systems primarily use coherent states for simplicity. However, squeezed states of light have been theoretically shown to offer significant advantages, including higher secret key rates, greater resilience to excess noise, and reduced requirements on information reconciliation efficiency. In this work, we experimentally verify these theoretical predictions and propose and demonstrate a practical squeezed-state CV-QKD system based on modern local-local oscillator and digital signal processing techniques. Operating over fiber channels and considering finite-size security against collective attacks, we show the advantages of our system over its coherent-state counterpart. Our work paves the way for squeezed states to become practical resources for quantum key distribution and other quantum information protocols.

arXiv:2506.19438•Science Advances•Oct 16, 2026•0 citations

Two-mode squeezing over deployed fiber coexisting with conventional communications

Joseph C. Chapman, Alexander Miloshevsky, Hsuan‐Hao Lu +3 more

Squeezed light is a crucial resource for continuous-variable (CV) quantum information science. Distributed multi-mode squeezing is critical for enabling CV quantum networks and distributed quantum sensing. To date, multi-mode squeezing measured by homodyne detection has been limited to single-room experiments without coexisting classical signals, i.e., on "dark" fiber. Here, after distribution through separate fiber spools (5 km), -0.9 ± 0.1-dB coexistent two-mode squeezing is measured. Moreover, after distribution through separate deployed campus fibers (about 250 m and 1.2 km), -0.5 ± 0.1-dB coexistent two-mode squeezing is measured. Prior to distribution, the squeezed modes are each frequency multiplexed with several classical signals-including the local oscillator and conventional network signals-demonstrating that the squeezed modes do not need dedicated dark fiber. After distribution, joint two-mode squeezing is measured and recorded for post-processing using triggered homodyne detection in separate locations. This demonstration enables future applications in quantum networks and quantum sensing that rely on distributed multi-mode squeezing.

arXiv:2304.10053•Optics Express•Jul 14, 2023•18 citations

Squeezed States Continuous-Variable Quantum Key Distribution Over 40 km Fibre with “Local” Local Oscillator

Huy Quang Nguyen, Ivan D. Derkach, Hou-Man Chin +5 more

Squeezed states promise significant enhancements to continuous-variable quantum key distribution (CV-QKD) systems; however, experimental demonstrations with real fibre channels remain elusive due to practical implementation challenges. Here, we propose and experimentally demonstrate a prepare-and-measure CV-QKD protocol utilising displaced squeezed states. We implemented this protocol over 40 km of single mode fibre with a free-running local local oscillator (LLO). Digital signal processing (DSP) was used for frequency and phase synchronization [1]. Figure 1: (a) experimental setup (b) digital signal processing procedure (c) secret key fraction calculation.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 23, 2025•0 citations

Remote Preparation of Bright Squeezed Light via Field-Deployed Multi-Core Fibers

Jintao Wang, Jinpeng Liao, Zhirong Chen +3 more

We developed a novel scheme for remote preparation of bright squeezed light using standard fiber-based components over field-deployed multi-core fibers. By implementing two phase-locked loops, we successfully generated bright amplitude-squeezed light over a 6 km laboratory single-mode fiber and a 17 km field-deployed multi-core fiber with measured squeezing levels of −2.52 dB and −1.80 dB, respectively. We also observed bright phase-squeezed light in the two scenarios with squeezing levels of −2.01 dB and −0.91 dB. We also measured results similar to those of the deployed fiber by using a 30 km laboratory single-mode fiber with comparable optical loss. The squeezed properties were confirmed with reconstructed Wigner functions using quantum state tomography. Our approach enabled remote users to access user-defined squeezed light based on a single seed laser, thereby maintaining coherence between their squeezed states, which could find applications in fiber-based quantum information processing and quantum metrology.

Journal of Lightwave Technology•Oct 8, 2024•1 citation
Squeezed light plays a vital role in quantum information processing. However, its highly sensitive nature presents significant practical challenges, particularly in remote detection, which traditionally requires complex systems such as active phase locking, clock synchronization, and polarization control. Here, we propose and demonstrate an asynchronous detection method for squeezed light eliminating the need for these complex systems. By employing radio-frequency heterodyne detection with a locally generated local oscillator and applying a series of digital unitary transformations, we successfully reconstruct squeezed states of light. We validate our approach in two key applications: the distribution of squeezed light over a 10 km fiber channel, and passive continuous-variables quantum key distribution based on squeezed vacuum states between two labs connected via deployed fiber. This demonstrates a practical digital reconstruction method for squeezed light, opening new avenues for practical distributed quantum sensing networks and high-performance, long-distance quantum communication using squeezed states.
Squeezed light plays a vital role in quantum information processing. By nature, it is highly sensitive, which presents significant practical challenges, particularly in remote detection, traditionally requiring complex systems such as active phase locking, clock synchronization, and polarization control. Here, we propose and demonstrate an asynchronous detection method for squeezed light that eliminates the need for these complex systems. By employing radio-frequency heterodyne detection with a locally generated local oscillator and applying a series of digital unitary transformations, we successfully reconstruct squeezed states of light. We validate the feasibility of our approach in two key applications: the distribution of squeezed light over a 10 km fiber channel, and secure quantum key distribution between two labs connected via deployed fiber based on continuous variables using squeezed vacuum states without active modulation. This demonstrates a practical digital reconstruction method for squeezed light, opening new avenues for practical distributed quantum sensing networks and high-performance and long-distance quantum communication using squeezed states and standard telecom technology.
Transmission and accurate detection of squeezed states of light will play a central role in the future quantum internet, where quantum cryptography, communication and computation will coexist in an organic system. Their coherent detection has recently proven to be crucial for photonics-based quantum computing [1] , and to provide improvements in continuous variables quantum key distribution [2] [6] and quantum sensing [3] . Often when measuring a quantum state through coherent detection, the local oscillator field is transmitted along with the signal; however, in realistic long-distance optical fiber transmissions, where the needed local oscillator optical power increases exponentially with the distance, the system’s performance deteriorates due to nonlinear Brillouin scattering, and wavelength multiplexing schemes may be needed to avoid the issue. Moreover, transmitting a local oscillator opens security loopholes in quantum key distribution systems, where an eavesdropper can defy the security assessment from the trusted parties by gaining control over the local oscillator [4] . It is therefore very important to design coherent detection schemes that make use of independent local oscillators. We demonstrate the transmission single-mode squeezed light at 1550 nm wavelength through single-mode optical fibers (10 m and 10 km lengths) and its homodyne detection, using an independent local oscillator and a real-time phase-control system. Fig. 1a depicts the implemented physical setup: 1550 nm squeezed light is generated through spontaneous parametric downconversion [5] , couples into a single-mode optical fiber and propagates towards the homodyne detector for quadrature measurement. Real-time phase control consists in detecting the interference between a 40 MHz single-sideband pilot mode -phase-locked to the downconverted pump- and the local oscillator, estimating their instantaneous phase difference and implementing a fast and broad FPGA-based phase control on the local oscillator. As shown in Fig. 1b and 1c, with the presented scheme it was possible to steadily measure up to 3.6 dB of squeezing after a 10 m optical fiber transmission, and up to 1.5 dB of squeezing after a 10 km fiber transmission, with similar performance in terms of phase error and control stability. The presented system is simple, robust and cost-effective, and it will represent a standard class of techniques to detect not only squeezed states of light, but any arbitrary quantum state of light, including Schrödinger cat states, highly useful in quantum computation and error correction.
Continuous-variable quantum key distribution (CV-QKD) has gathered significant interest for its potential to achieve high secret key rates and seamless integration with existing optical communication infrastructure. State-of-the-art CV-QKD systems primarily use coherent states for simplicity. However, squeezed states of light have been theoretically shown to offer significant advantages, including higher secret key rates, greater resilience to excess noise, and reduced requirements on information reconciliation efficiency. In this work, we experimentally verify these theoretical predictions and propose and demonstrate a practical squeezed-state CV-QKD system based on modern local-local oscillator and digital signal processing techniques. Operating over fiber channels and considering finite-size security against collective attacks, we show the advantages of our system over its coherent-state counterpart. Our work paves the way for squeezed states to become practical resources for quantum key distribution and other quantum information protocols.
Squeezed light is a crucial resource for continuous-variable (CV) quantum information science. Distributed multi-mode squeezing is critical for enabling CV quantum networks and distributed quantum sensing. To date, multi-mode squeezing measured by homodyne detection has been limited to single-room experiments without coexisting classical signals, i.e., on "dark" fiber. Here, after distribution through separate fiber spools (5 km), -0.9 ± 0.1-dB coexistent two-mode squeezing is measured. Moreover, after distribution through separate deployed campus fibers (about 250 m and 1.2 km), -0.5 ± 0.1-dB coexistent two-mode squeezing is measured. Prior to distribution, the squeezed modes are each frequency multiplexed with several classical signals-including the local oscillator and conventional network signals-demonstrating that the squeezed modes do not need dedicated dark fiber. After distribution, joint two-mode squeezing is measured and recorded for post-processing using triggered homodyne detection in separate locations. This demonstration enables future applications in quantum networks and quantum sensing that rely on distributed multi-mode squeezing.
Squeezed states promise significant enhancements to continuous-variable quantum key distribution (CV-QKD) systems; however, experimental demonstrations with real fibre channels remain elusive due to practical implementation challenges. Here, we propose and experimentally demonstrate a prepare-and-measure CV-QKD protocol utilising displaced squeezed states. We implemented this protocol over 40 km of single mode fibre with a free-running local local oscillator (LLO). Digital signal processing (DSP) was used for frequency and phase synchronization [1]. Figure 1: (a) experimental setup (b) digital signal processing procedure (c) secret key fraction calculation.
We developed a novel scheme for remote preparation of bright squeezed light using standard fiber-based components over field-deployed multi-core fibers. By implementing two phase-locked loops, we successfully generated bright amplitude-squeezed light over a 6 km laboratory single-mode fiber and a 17 km field-deployed multi-core fiber with measured squeezing levels of −2.52 dB and −1.80 dB, respectively. We also observed bright phase-squeezed light in the two scenarios with squeezing levels of −2.01 dB and −0.91 dB. We also measured results similar to those of the deployed fiber by using a 30 km laboratory single-mode fiber with comparable optical loss. The squeezed properties were confirmed with reconstructed Wigner functions using quantum state tomography. Our approach enabled remote users to access user-defined squeezed light based on a single seed laser, thereby maintaining coherence between their squeezed states, which could find applications in fiber-based quantum information processing and quantum metrology.