146 research outputs found
Time-Domain Universal Linear-Optical Operations for Universal Quantum Information Processing
We demonstrate universal and programmable three-mode linear optical
operations in the time domain by realizing a scalable dual-loop optical circuit
suitable for universal quantum information processing (QIP). The
programmability, validity, and deterministic operation of our circuit are
demonstrated by performing nine different three-mode operations on
squeezed-state pulses, fully characterizing the outputs with variable
measurements, and confirming their entanglement. Our circuit can be scaled up
just by making the outer loop longer and also extended to universal quantum
computers by incorporating feedforward systems. Thus, our work paves the way to
large-scale universal optical QIP
Programmable time-multiplexed squeezed light source
One of the leading approaches to large-scale quantum information processing
(QIP) is the continuous-variable (CV) scheme based on time multiplexing (TM).
As a fundamental building block for this approach, quantum light sources to
sequentially produce time-multiplexed squeezed-light pulses are required;
however, conventional CV TM experiments have used fixed light sources that can
only output the squeezed pulses with the same squeezing levels and phases. We
here demonstrate a programmable time-multiplexed squeezed light source that can
generate sequential squeezed pulses with various squeezing levels and phases at
a time interval below 100 ns. The generation pattern can be arbitrarily chosen
by software without changing its hardware configuration. This is enabled by
using a waveguide optical parametric amplifier and modulating its continuous
pump light. Our light source will implement various large-scale CV QIP tasks.Comment: 14 pages, 7 figure
Optimization of quantum noise in space gravitational-wave antenna DECIGO with optical-spring quantum locking considering mixture of vacuum fluctuations in homodyne detection
Quantum locking using optical spring and homodyne detection has been devised
to reduce quantum noise that limits the sensitivity of DECIGO, a space-based
gravitational wave antenna in the frequency band around 0.1 Hz for detection of
primordial gravitational waves. The reduction in the upper limit of energy
density from to
, as inferred from recent observations, necessitates
improved sensitivity in DECIGO to meet its primary science goals. To accurately
evaluate the effectiveness of this method, this paper considers a detection
mechanism that takes into account the influence of vacuum fluctuations on
homodyne detection. In addition, an advanced signal processing method is
devised to efficiently utilize signals from each photodetector, and design
parameters for this configuration are optimized for the quantum noise. Our
results show that this method is effective in reducing quantum noise, despite
the detrimental impact of vacuum fluctuations on its sensitivity.Comment: 12 pages, 5 figure
First-step experiment in developing optical-spring quantum locking for DECIGO: sensitivity optimization for simulated quantum noise by completing the square
DECi-hertz Interferometer Gravitational Wave Observatory (DECIGO) is a future
mission for a space-borne laser interferometer. DECIGO has 1,000-km-long arm
cavities mainly to detect the primordial gravitational waves (PGW) at lower
frequencies around 0.1 Hz. Observations in the electromagnetic spectrum have
lowered the bounds on the upper limit of PGW energy density (). As a result, DECIGO's target sensitivity, which
is mainly limited by quantum noise, needs further improvement. To maximize the
feasibility of detection while constrained by DECIGO's large diffraction loss,
a quantum locking technique with an optical spring was theoretically proposed
to improve the signal-to-noise ratio of the PGW. In this paper, we
experimentally verify one key element of the optical-spring quantum locking:
sensitivity optimization by completing the square of multiple detector outputs.
This experiment is operated on a simplified tabletop optical setup with
classical noise simulating quantum noise. We succeed in getting the best of the
sensitivities with two different laser powers by the square completion method.Comment: 10 pages, 14 figure
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