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Europhysics Letters (EPL)

Quantum nondemolition measurements and generation of individually squeezed twin beams by a degenerate optical parametric amplifier

Stephan Schiller, Robert Bruckmeier, Manfred Schalke, K Schneider, J. Mlynek

Published Nov 10, 1996• 16 citations
Publisher

Abstract

A novel scheme for continuous-wave quantum nondemolition (QND) detection of optical-amplitude quadratures is implemented using a degenerate optical parametric amplifier. A monolithic ring resonator with optimizable frustrated total internal reflection coupling is used. Signal and meter output beams are squeezed by 0.5 dB and 2.2 dB, and 38% correlated. This implies the first realization of individually squeezed twin beams, as well as quantum state preparation ability for both output beams. A quantum optical tap efficiency T s + T m = 1.08 is achieved. The all-solid-state system was completely stabilized and continuously operated as a QND device for up to 36 hours.

DOI
10.1209/epl/i1996-00236-0

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A novel scheme for continuous-wave quantum nondemolition (QND) detection of optical-amplitude quadratures is implemented using a degenerate optical parametric amplifier. A monolithic ring resonator with optimizable frustrated total internal reflection coupling is used. Signal and meter output beams are squeezed by 0.5 dB and 2.2 dB, and 38% correlated. This implies the first realization of individually squeezed twin beams, as well as quantum state preparation ability for both output beams. A quantum optical tap efficiency T s + T m = 1.08 is achieved. The all-solid-state system was completely stabilized and continuously operated as a QND device for up to 36 hours.
Continuous quantum nondemolition (QND) measurements of the amplitude quadrature of a 1064 nm wave are performed with a monolithic dual-port degenerate optical parametric amplifier (OPA). The quality of the measurement is limited in part by the quantum fluctuations carried by the vacuum meter input wave. Improved QND measurements are realized by injecting 3.4 dB amplitude-squeezed light into the meter input port of the OPA. This achieves increased squeezing and correlation of the output signal and meter waves, and both improved operation as a quantum optical tap and as a quantum state preparator. The all-solid-state system was operated for 5 h with high stability.
Summary form only given. Quantum nondemolition (QND) measurements seek to measure a quantum mechanical observable precisely without disturbing the observable itself and its time evolution. They are of great importance in precision metrology and information processing at the quantum level. In this work, a new QND scheme for optical continuous-wave measurements of quadrature observables using a degenerate, type-I phasematched, dual port, optical parametric amplifier (OPA), is implemented. We employ a low-loss monolithic MgO:LiNbO/sub 3/ ring resonator.
Optical quantum nondemolition measurements are performed using a beamsplitter with a nonclassical meter input and a electro-optic feedforward loop. The nonclassical meter input is provided by a stable 4.5 dB amplitude squeezed source generated by an optical parametric amplifier. We show that the implementation of a feedforward loop gives a substantial improvement in the signal transfer efficiency. With a 92% reflective beamsplitter we measure a transfer coefficient of Ts+m = 1.81. The quantum state preparation ability of our system is evaluated using two-dimensional correlation plots. This technique allows the direct visualization of the quantum correlations between the outputs of the QND system.
The bright Einsten-Podolsky-Rosen (EPR) beams with the quantum correlations between the quadrature-phase amplitudes of the spatially separated signal and idler beams have been experimentally generated from a cw nondegenerate optical parametric amplifier injected by seed waves with degenerate frequency but orthogonal polarization. The correlation degree of $0.853\ifmmode\pm\else\textpm\fi{}0.004$ between the quadrature-phase amplitudes of the output entangled beams is directly inferred from the measured quadrature-phase squeezing of the output vacuum squeezed-state light field formed from superposition of the original signal and idler modes. Our theoretical calculation and experimental measurements provide a reliable method to confirm the quadrature phase-squeezing and EPR correlation of bright light field.