Changde Xie

Quantum variances and squeezing of output field from NOPA

Abstract The quadrature phase squeezing of coupled-mode and intensity difference squeezing between signal and idler mode of output field from continuous nondegenerate optical parametric amplifier (NOPA) are theoretically analyzed and compared. The calculation results provide design references for nonclassical light generation system.

Entanglement swapping using nondegenerate optical parametric amplifier

Abstract We introduce a simple, experimentally realizable, entanglement swapping protocol for continuous variables by exploring nondegenerate optical parametric amplifier. Due to adopting the bright EPR beams and the simple direct measurement for Bell-state, the entanglement swapping and the verification of entanglement swapping is within the reach of current technology and significantly simplify the implementation.

CW Nd:MgO:LiNbO/sub 3/ self-frequency-doubling laser at room temperature

A CW Nd:MgO:LiNbO/sub 3/ self-frequency-doubling laser has been demonstrated at room temperature for the first time. The second-harmonic output at lambda =547 nm up to 18 mW was achieved in a simple resonator. >

High-Power Low-Noise Nd:YAP/LBO Laser With Dual Wavelength Outputs

A high-power single-frequency Nd:YAP/LBO laser with stable dual wavelength outputs is designed and built. The laser resonator satisfying optimal coupling condition for second-harmonic generation is in a configuration of a figure “8” shaped ring cavity consisting of two convex mirrors and two concave mirrors. An additional wedge YVO4 crystal is inserted in the resonator to act as a polarizer, so that the stability of the laser operation is improved. The maximum output powers of 4.5 W at 540 nm and 1.5 W at 1080 nm are simultaneously achieved. The measured power stabilities of the fundamental wave and the second-harmonic wave are ±0.32% and ±0.6% for 3 h, respectively.

Investigation of the characteristics of the intensity noise of singly resonant active second-harmonic generation

We derive analytical expressions for the quantum-noise spectra of a singly resonant active frequency-doubling laser with single-frequency operation by using a linearized input–output method. For operation of a practical solid-state laser, we analyze separately the contributions of the various noise sources to the final spectrum. The change in resonance in the spectrum from an overdamped- (at higher μ) to an underdamped- (at smaller μ) driven second-order oscillator where μ is the nonlinear coupling coefficient, was experimentally observed with a diode-pumped Nd:YVO4+KTP single-frequency-doubling laser. The experimental result is in good agreement with the theoretical expectation.

Single-Frequency

A high-power single-frequency laser at 671 and 1342 nm is designed and built. We find that for a high power Nd:YVO4 laser, the thermal load of gain medium at 1342 nm lasing is much more stronger than that without lasing, which results in a bistability-like phenomenon on the relation curve between the output power and pump power. Based on the consideration to this special phenomenon, in our design, the cavity parameters are optimized carefully to satisfy the laser stability condition for both cases before and after lasing, the thermal effect of the Nd:YVO4 crystal is mitigated by increasing appropriately the fundamental mode size. The maximal output powers of 2.8 W at 671 nm and 850 mW at 1342 nm are simultaneously achieved.

{\rm Nd}{:}{\rm YVO}_{4}

Abstract A simple scheme to realize quantum teleportation with π/2 unitarily rotated transformation for continuous variable is proposed, in which the bright entangled EPR beam is produced by phase sensitive nondegenerate optical parametric amplifier with a fixed relative phase of π/4 between the subharmonic signal and the harmonic pump field. The measurement of “Bell state” is accomplished by means of direct detection of photocurrents.

Laser at 671 nm With High-Output Power of 2.8 W

We investigate the different characteristics of the intensity noise of a laser-diode-pumped single-frequency ring Nd:YVO (4) laser and a Nd:YVO (4)-KTP green laser. By use of an optoelectronic feedback circuit connected directly to the pump current of the laser diode, the low-frequency intensity noise of the intracavity frequency doubler was suppressed to some extent.

Quantum teleportation for continuous variables by means of a phase sensitive nondegenerate optical parametric amplifier

We develop a scheme to reconstruct the optical quantum state of a single-mode bright light field by using the dispersion characteristics of the empty cavity. The input field has a strong coherent component at frequency ω0, which serves as a local oscillator (LO) to measure its two-sideband mode at ω0±Ω. We control the relative phase of the 0–2π range between the LO and the two-sideband mode by scanning the cavity length, so the optical quantum state is tomographically reconstructed. In the proposed scheme the influence of the space-mode mismatch between the LO and measured mode on the quantum efficiency is eliminated, and this scheme can conveniently be used in some quantum optical systems in which LO field cannot be available.

Suppression of the intensity noise of a laser-diode-pumped single-frequency ring Nd:YVO(4)-KTP green laser by optoelectronic feedback.

Summary form only given. Two pairs of EPR beams with identical frequency and constant phase relation are composed on two beamsplitters to produce two pairs of conditional entangled beams, two halves of which are sent to two sending stations (Alices) and others to two receiving stations (Bobs). The EPR entangled beams initially result from two-mode quadrature squeezed state light produced by, for example, two nondegenerate optical parametric oscillators (NOPO) pumped by a same laser. Converting the squeezed component of one of the EPR sources between amplitude and phase, the input quantum state at a sender will be reproduced at two receivers in turn. The quantum switching performance between two receivers is only manipulated by the squeezed component of a two-mode squeezed state light, which can be experimentally demonstrated by controlling the parametric process either in amplification or deamplification.