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Advanced Quantum Technologies

Generation of Picosecond Pulsed Bright Squeezed Light With Perfect Vortex Distribution

Jun Liu, Yan Liu, Xiaowei Wu, Xiaolong Su

Published Jun 1, 2026• 0 citations
Publisher

Abstract

ABSTRACT Broadband bright squeezed states are important quantum resources that play a crucial role in quantum information and quantum measurement. Here, we present the broadband bright pulsed squeezed states generated by a single‐pass optical parametric amplification based on a custom‐poled potassium titanyl phosphate crystal. By optimizing the spatial mode of the picosecond pump beams, a bright squeezed light with 1.7 dB squeezing and output power of 5 mW is obtained. With a spatial light modulator, the spatial distribution of the bright squeezed light is shaped into perfect vortex beams with topological charges up to , while the squeezing level is 1.4 dB. The presented squeezed states provide essential resources for advanced quantum optics applications. Graphical Abstract

DOI
10.1002/qute.70334

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ABSTRACT Broadband bright squeezed states are important quantum resources that play a crucial role in quantum information and quantum measurement. Here, we present the broadband bright pulsed squeezed states generated by a single‐pass optical parametric amplification based on a custom‐poled potassium titanyl phosphate crystal. By optimizing the spatial mode of the picosecond pump beams, a bright squeezed light with 1.7 dB squeezing and output power of 5 mW is obtained. With a spatial light modulator, the spatial distribution of the bright squeezed light is shaped into perfect vortex beams with topological charges up to , while the squeezing level is 1.4 dB. The presented squeezed states provide essential resources for advanced quantum optics applications. Graphical Abstract
We report the generation of squeezed vacuum states of light at 1550 nm with a broadband quantum noise reduction of up to 4.8 dB ranging from 5 MHz to 1.2 GHz sideband frequency. We used a custom-designed 2.6 mm long biconvex periodically-poled potassium titanyl phosphate (PPKTP) crystal. It featured reflectively coated end surfaces, 2.26 GHz of linewidth and generated the squeezing via optical parametric amplification. Two homodyne detectors with different quantum efficiencies and bandwidths were used to characterize the non-classical noise suppression. We measured squeezing values of up to 4.8 dB from 5 to 100 MHz and up to 3 dB from 100 MHz to 1.2 GHz. The squeezed vacuum measurements were limited by detection loss. We propose an improved detection scheme to measure up to 10 dB squeezing over 1 GHz. Our results of GHz bandwidth squeezed light generation provide new prospects for high-speed quantum key distribution.
A squeezed state is a key quantum resource for quantum information processing and quantum metrology. It is essential to extend the dimension of the squeezed state for spatially multiplexed large-capacity quantum communication and quantum precision measurements. Here, we report the experimental preparation of a picosecond pulsed squeezed state carrying orbital angular momentum (OAM). By modulating bright pulsed squeezed light with a spatial light modulator, we generate a squeezed state with Laguerre-Gaussian distribution, whose topological charges are up to l = 20 and squeezed noise is 1.22 dB below the shot noise level. The presented bright picosecond pulsed squeezed light carrying high-order OAM provides promising resources for high-dimensional quantum information processing.
We demonstrate experimentally the short pulse amplitude squeezed light from a singly resonant synchronously pumped optical parametric oscillator (SPOPO). The SPOPO operates in the frequency degenerate case and below threshold, with using a periodically poled potassium titanyl phosphate crystal. The pump laser is the second harmonic of a ultrashort mode-locked femtosecond pulse at 850 nm. The reduction of quantum noise of 2.58 dB is obtained experimentally. The squeezing extent is deduced to be 4.48 dB.
Squeezed states of light enable enhanced measurement precision by reducing noise below the standard quantum limit. A key application of squeezed light is nonlinear microscopy, where state-of-the-art performance is limited by photodamage and quantum-limited noise. Such microscopes require bright, pulsed light for optimal operation, yet generating and detecting bright pulsed squeezing at high levels remains challenging. In this work, we present an efficient technique to generate high levels of bright picosecond pulsed squeezed light using a χ2χ^2χ2 optical parametric amplification process in a waveguide. We measure −3.2 dB-3.2~\mathrm{dB}−3.2 dB of bright squeezing with optical power compatible with nonlinear microscopy, as well as −3.6 dB-3.6~\mathrm{dB}−3.6 dB of vacuum squeezing. Corrected for losses, these squeezing levels correspond to −15.4−8.7+2.7 dB-15.4^{+2.7}_{-8.7}~\mathrm{dB}−15.4−8.7+2.7​ dB of squeezing generated in the waveguide. The measured level of bright amplitude pulsed squeezing is to our knowledge the highest reported to date, and will contribute to the broader adoption of quantum-enhanced nonlinear microscopy in biological studies.
We report the generation of squeezed vacuum states of light at 1550 nm with a broadband quantum noise reduction of up to 4.8 dB ranging from 5 MHz to 1.2 GHz sideband frequency. We used a custom-designed 2.6 mm long biconvex periodically-poled potassium titanyl phosphate (PPKTP) crystal. It featured reflectively coated end surfaces, 2.26 GHz of linewidth and generated the squeezing via optical parametric amplification. Two homodyne detectors with different quantum efficiencies and bandwidths were used to characterize the non-classical noise suppression. We measured squeezing values of up to 4.8 dB from 5 to 100 MHz and up to 3 dB from 100 MHz to 1.2 GHz. The squeezed vacuum measurements were limited by detection loss. We propose an improved detection scheme to measure up to 10 dB squeezing over 1 GHz. Our results of GHz bandwidth squeezed light generation provide new prospects for high-speed quantum key distribution.
Hybrid quantum photonics seeks to combine the complementary advantages of continuous- and discrete-variable quantum optics. This typically entails photon-counting measurements on entangled states generated by interfering many single-mode squeezed-vacuum (SMSV) states. However, because conventional photon-counting schemes are mode-insensitive, it is critical that the SMSV states occupy a single, well-defined mode. Achieving this requires careful engineering of the process, which determines both the spatial and spectro-temporal properties of the generated state. In addition, the ideal source must be massively scalable, capable of efficiently generating strong squeezing, and remain compatible with existing detection schemes and fiber networks. Although many platforms address one or more of these requirements, satisfying all of them simultaneously remains challenging. Here, we present a source that meets all of these requirements: a single-pass, periodically poled, Type-II potassium titanyl phosphate (KTP) waveguide optimized for scalable hybrid quantum-photonic architectures. The SMSV state produced by the source has a measured effective mode number of 1.24. Furthermore, the source is extremely bright (producing up to 40 000 photons per pulse) and operates at a central wavelength of 1546nm, optimized for fiber-network compatibility and which, in combination with picosecond duration, also enables intrinsic photon-number resolution in superconducting nanowire single-photon detectors. Although this source constitutes an ideal source in a simplified picture, the ultimate limitations of any source will be governed by complex dynamics that arise when the system is driven at high-gain or due to unavoidable loss during state generation. We have therefore developed a complete theoretical framework that enables a comprehensive photon-counting-based characterization of the source.