Abstract
Phase-sensitive detection is the essential projective measurement for measurement-based continuous-variable quantum information processing. The bandwidth of conventional electrical phase-sensitive detectors is up to several gigahertz, which would limit the speed of quantum computation. It is theoretically proposed to realize terahertz-order detection bandwidth by using all-optical phase-sensitive detection with an optical parametric amplifier (OPA). However, there have been experimental obstacles to achieve large parametric gain for continuous waves, which is required for use in quantum computation. Here, we adopt a fiber-coupled χ(2) OPA made of a periodically poled LiNbO3 waveguide with high durability for intense continuous-wave pump light. Thanks to that, we manage to detect quadrature amplitudes of broadband continuous-wave squeezed light. 3 dB of squeezing is measured up to 3 THz of sideband frequency with an optical spectrum analyzer. Furthermore, we demonstrate the phase-locking and dispersion compensation of the broadband continuous-wave squeezed light, so that the phase of the squeezed light is maintained over 1 THz. The ultra-broadband continuous-wave detection method and dispersion compensation would help to realize all-optical quantum computation with over-THz clock frequency.
Highlights
All-optical quantum computation is an ultimate goal of the research of quantum information processing which pursues speed of computation
Optical parametric amplifiers (OPAs) made of nonlinear media play a role in converting quantum field of light into loss-tolerant “classical” field, which can be directly used for feed-forward control
We demonstrate dispersion compensation of the broadband squeezed light, and the phase of the squeezed light is maintained over 1 THz
Summary
All-optical quantum computation is an ultimate goal of the research of quantum information processing which pursues speed of computation. The speed of quantum computation is determined by the bandwidths of the generated entangled state, detection and feed-forward control. Optical parametric amplifiers (OPAs) made of nonlinear media play a role in converting quantum field of light into loss-tolerant “classical” field, which can be directly used for feed-forward control. Amplified light is tolerant to optical loss [25], so that it can be converted into electrical signals with broadband low-quantum-efficiency detector [24] or directly used for alloptical feed-forward control [6, 26]. The bandwidth of the measured squeezed light was limited by chromatic dispersion in the experiment, which might be an obstacle to realize ultra-fast quantum information processing. Our work would contribute to the realization of all-optical quantum computing with over-THz clock frequency
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