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

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)

Quantum entanglement in strongly non-degenerate OPOs: The doubly and singly resonant cases

Domenico Cuozzo, John Jeffers, Gian‐Luca Oppo

Published May 1, 2011• 0 citations
Publisher

Abstract

Many theoretical and experimental approaches to quantum entanglement in Optical Parametric Oscillators (OPO) concern the degenerate or the slightly non-degenerate cases where a single local oscillator can be used to measure quadrature correlations for the characterization of fluctuations below the Standard Quantum Limit (SQL) in the frequency domain. In the strongly non-degenerate case, alternative characterizations of quantum entanglement are needed. We provide evidence that correlation functions corresponding to coincidence measurements of the intensity difference between signal and idler fields should be able to assess quantum entanglement and at the same time be experimentally viable in the case of strongly non-degenerate OPO.

DOI
10.1109/cleoe.2011.5943380

Related papers

Quantum Imagess in Non Degenerate Optical Parametric Oscillators

C. Szwaj, Gian‐Luca Oppo

Quantum images, that is inhomogeneous field distributions purely generated by quantum fluctuations, persist when passing from the degenerate to the non-degenerate case of optical parametric oscillators (OPO). Below the threshold for parametric oscillation where the near-field distributions are homogeneous both in intensity and phase, appropriate spatial correlation functions anticipate the transverse spatial pattern that appears above threshold. In particular, the angular dependence of the far field spatial correlation function is able to reveal the travelling-wave nature of the phase pattern above threshold typical of nondegenerate OPOs. Cross-correlation functions between signal and idler intensities show clear evidence of the non-classical nature of the output light.

European Quantum Electronics Conference (EQEC)•Aug 24, 2005•0 citations

Experimental evidence of entanglement between intense beams produced by a non-degenerate OPO above threshold

Alessandro S. Villar, Luciano Soares da Cruz, K. N. Cassemiro +2 more

In this work, first measurements that indicate entanglement between non-degenerate signal and idler beams above threshold are presented. These curves are obtained synchronously varying analysis cavities' lengths around their resonances.

European Quantum Electronics Conference (EQEC)•Jan 18, 2006•0 citations

Quantum correlations of quadrature amplitudes in nondegenerate parametric downconversion

Silvania F. Pereira, K. C. Peng, Harry J. Kimble

For measurements describable by a discrete set of possibilities, numerous demonstrations of the violation of Bell's inequalities have been reported in optical physics based on observations of polarization correlations for photon pairs. By contrast for observables with a continuous spectrum, there appears to be no general inequalities corresponding to those of Bell and no experimental realization of the original Einstein-Podolsky-Rosen paradox. Following Reid and Drummond,1 we are attempting to demonstrate the EPR paradox in the context of the measurement of continuous quantum variables with a subthreshold optical parametric oscillator operated in a frequency degenerate but polarization nondegenerate mode. In this case, the EPR paradox is formulated in terms of two sets of quadrature phase amplitudes for the spatially separated signal and idler fields. As the parametric gain is increased toward threshold, the quadrature amplitudes of the signal and idler beams become increasingly faithful quantum copies of one another. Our measurements of quadrature amplitudes are carried out using independent balanced homodyne detectors at two sites. When operated for the detection of squeezing at one site, noise reductions of 4 dB relative to the vacuum state limit are observed, which is most encouraging since noise reductions >3 dB in the difference photocurrent from the two sites are sufficient for inference at a distance of a signal observable from a measurement of the corresponding idler variable.

Annual Meeting Optical Society of America•Jan 1, 1989•0 citations

Entanglement in the above-threshold optical parametric oscillator

Alessandro S. Villar, K. N. Cassemiro, K. Dechoum +3 more

We investigate entanglement in the above-threshold optical parametric oscillator, both theoretically and experimentally, and discuss its potential applications to quantum information. The fluctuations measured in the subtraction of signal and idler amplitude quadratures are Δ2p̂−=0.50(1), or −3.01(9) dB, and in the sum of phase quadratures they are Δ2q̂+=0.73(1), or −1.37(6) dB. A detailed experimental study of the noise behavior as a function of pump power is presented, and the discrepancies with theory are discussed.

arXiv:quant-ph/0610208•Journal of the Optical Society of America B•Jan 26, 2007•44 citations

Two-colour quantum entanglement in a singly resonant optical parametric oscillator approaching threshold

Domenico Cuozzo, Gian‐Luca Oppo

Following the analytical work of Ref. [1], a numerical analysis of squeezing and quantum entanglement in a continuous wave singly-resonant optical parametric oscillator approaching threshold is provided. The singly resonant case is mainly relevant to largely non-degenerate signal and idler modes (two-colour output). As the threshold of oscillation is approached the numerical spectra of the intensity difference confirm squeezing of quantum fluctuations and a progressive line-narrowing in the linear case. In the nonlinear case entanglement is confirmed although progressively reduced when approaching threshold with the squeezing spectra still displaying a narrowing of the spectral line. Modification of quantum entanglement approaching threshold is also evaluated via the condition of state inseparability.

The European Physical Journal D•Jan 1, 2012•0 citations

Degenerate parametric oscillator

P. D. Drummond, Mark S. Hillery

The optical parametric oscillator is one of the most well-characterized devices in nonlinear optics, with many useful applications, especially as a frequency converter and as a wide-band amplifier. Novel discoveries made with these devices in the quantum domain include demonstrations of large amounts of both single-mode and two-mode squeezing, and, in the two-mode case, significant quantum intensity correlations between the two modes and quadrature correlations, which provided the first experimental demonstration of the original Einstein–Podolsky–Rosen (EPR) paradox. In this chapter, a systematic theory is developed of quantum fluctuations in the degenerate parametric oscillator. The quantum statistical effects produced by the degenerate parametric amplifier and oscillator have been intensely studied. As we have seen, the amount of transient squeezing produced in an ideal lossless parametric amplifier was calculated using asymptotic methods by Crouch and Braunstein. It was found to scale inversely with the square root of the initial pump photon number. When the system is put into a cavity, and driving and dissipation are introduced, we find that the steady state of a driven degenerate parametric oscillator bifurcates. There is a single steady state at low driving strengths, but, as the driving field increases, a threshold value is reached and the single state splits and forms two stable states. Below the threshold, a linearized analysis of squeezing in the quantum quadratures is possible; while above this threshold, or critical point, the tunneling time between the two states due to quantum fluctuations can be calculated.

Cambridge University Press eBooks•Mar 27, 2014•0 citations
Many theoretical and experimental approaches to quantum entanglement in Optical Parametric Oscillators (OPO) concern the degenerate or the slightly non-degenerate cases where a single local oscillator can be used to measure quadrature correlations for the characterization of fluctuations below the Standard Quantum Limit (SQL) in the frequency domain. In the strongly non-degenerate case, alternative characterizations of quantum entanglement are needed. We provide evidence that correlation functions corresponding to coincidence measurements of the intensity difference between signal and idler fields should be able to assess quantum entanglement and at the same time be experimentally viable in the case of strongly non-degenerate OPO.
Quantum images, that is inhomogeneous field distributions purely generated by quantum fluctuations, persist when passing from the degenerate to the non-degenerate case of optical parametric oscillators (OPO). Below the threshold for parametric oscillation where the near-field distributions are homogeneous both in intensity and phase, appropriate spatial correlation functions anticipate the transverse spatial pattern that appears above threshold. In particular, the angular dependence of the far field spatial correlation function is able to reveal the travelling-wave nature of the phase pattern above threshold typical of nondegenerate OPOs. Cross-correlation functions between signal and idler intensities show clear evidence of the non-classical nature of the output light.
For measurements describable by a discrete set of possibilities, numerous demonstrations of the violation of Bell's inequalities have been reported in optical physics based on observations of polarization correlations for photon pairs. By contrast for observables with a continuous spectrum, there appears to be no general inequalities corresponding to those of Bell and no experimental realization of the original Einstein-Podolsky-Rosen paradox. Following Reid and Drummond,1 we are attempting to demonstrate the EPR paradox in the context of the measurement of continuous quantum variables with a subthreshold optical parametric oscillator operated in a frequency degenerate but polarization nondegenerate mode. In this case, the EPR paradox is formulated in terms of two sets of quadrature phase amplitudes for the spatially separated signal and idler fields. As the parametric gain is increased toward threshold, the quadrature amplitudes of the signal and idler beams become increasingly faithful quantum copies of one another. Our measurements of quadrature amplitudes are carried out using independent balanced homodyne detectors at two sites. When operated for the detection of squeezing at one site, noise reductions of 4 dB relative to the vacuum state limit are observed, which is most encouraging since noise reductions >3 dB in the difference photocurrent from the two sites are sufficient for inference at a distance of a signal observable from a measurement of the corresponding idler variable.
We investigate entanglement in the above-threshold optical parametric oscillator, both theoretically and experimentally, and discuss its potential applications to quantum information. The fluctuations measured in the subtraction of signal and idler amplitude quadratures are Δ2p̂−=0.50(1), or −3.01(9) dB, and in the sum of phase quadratures they are Δ2q̂+=0.73(1), or −1.37(6) dB. A detailed experimental study of the noise behavior as a function of pump power is presented, and the discrepancies with theory are discussed.
Following the analytical work of Ref. [1], a numerical analysis of squeezing and quantum entanglement in a continuous wave singly-resonant optical parametric oscillator approaching threshold is provided. The singly resonant case is mainly relevant to largely non-degenerate signal and idler modes (two-colour output). As the threshold of oscillation is approached the numerical spectra of the intensity difference confirm squeezing of quantum fluctuations and a progressive line-narrowing in the linear case. In the nonlinear case entanglement is confirmed although progressively reduced when approaching threshold with the squeezing spectra still displaying a narrowing of the spectral line. Modification of quantum entanglement approaching threshold is also evaluated via the condition of state inseparability.
The optical parametric oscillator is one of the most well-characterized devices in nonlinear optics, with many useful applications, especially as a frequency converter and as a wide-band amplifier. Novel discoveries made with these devices in the quantum domain include demonstrations of large amounts of both single-mode and two-mode squeezing, and, in the two-mode case, significant quantum intensity correlations between the two modes and quadrature correlations, which provided the first experimental demonstration of the original Einstein–Podolsky–Rosen (EPR) paradox. In this chapter, a systematic theory is developed of quantum fluctuations in the degenerate parametric oscillator. The quantum statistical effects produced by the degenerate parametric amplifier and oscillator have been intensely studied. As we have seen, the amount of transient squeezing produced in an ideal lossless parametric amplifier was calculated using asymptotic methods by Crouch and Braunstein. It was found to scale inversely with the square root of the initial pump photon number. When the system is put into a cavity, and driving and dissipation are introduced, we find that the steady state of a driven degenerate parametric oscillator bifurcates. There is a single steady state at low driving strengths, but, as the driving field increases, a threshold value is reached and the single state splits and forms two stable states. Below the threshold, a linearized analysis of squeezing in the quantum quadratures is possible; while above this threshold, or critical point, the tunneling time between the two states due to quantum fluctuations can be calculated.