Quantum Nondemolition Measurement Of Photon Number Research Articles

Quantum-nondemolition measurements with coherent soliton probes.

We obtain bounds on the signal-to-noise ratio for quantum-nondemolition measurement of photon number, using soliton collisions. A combined phase and amplitude quadrature measurement strategy can give almost noise-free results, provided equal amplitude solitons with low relative velocities are used.

Quantum-nondemolition measurement of photon number using radiation pressure.

We propose a quantum-nondemolition measurement of the amplitude quadrature and the photon-number statistics by using the effect of radiation pressure on a freely suspended mirror. We propose to measure the momentum fluctuations of the mirror which will give us a readout of the amplitude quadrature fluctuations. The scheme we propose is able to avoid the back-action noise leaving the state of the field after the measurement practically undegraded.

Lie-algebra methods in quantum optics: The Liouville-space formulation.

Lie-algebra methods for investigating quantum optical systems are presented within the framework of the Liouville-space formulation. The generalized decomposition formulas for exponential functions of the generators of su(2) and su(1,1) Lie algebras are derived and their expectation values are calculated for typical states in quantum optics. The general procedure for using Lie algebras in the Liouville space to treat quantum optical processes is given in terms of generalized decomposition formulas and their use is demonstrated by calculating the absorption line shape and photon echo signal in a localized electron-phonon system. It is also shown that the photon-counting probability can be calculated by using the su(1,1) Lie algebra and that the electron-counting probability can be calculated by using the su(2) Lie algebra. The su(1,1) Lie algebra is also used to investigate a quantum-nondemolition measurement of photon number in the four-wave-mixing model.

Compensation of self-phase modulation in a QND measurement of photon number based on the optical Kerr effect

The authors study a quantum non-demolition (QND) set-up for the measurement of photon number, employing the optical Kerr effect. A method for the compensation of the negative effects of self-phase modulation is discussed. Losses are taken into account. It is seen that the performance of the device is limited in the first place by losses, rather than by self-phase modulation.

Continuous quantum-nondemolition measurement of photon number.

This paper presents a general theory for a continuous quantum-nondemolition measurement of photon number. This theory treats a time-distributed measurement as a sequence of measurements in which at most one photon can be detected in an infinitesimal time, and shows that the average number of photons remaining in the measured field increases when a photon is detected and decreases when no photon is detected. The state of the measured system evolves nonunitarily and reduces continuously to a number state whose eigenvalue is uniquely determined by the average rate of photodetection and whose probability distribution coincides with the initial photon-number distribution

Quantum Zeno effect induced by quantum-nondemolition measurement of photon number.

Measurements performed on a system will alter the dynamics of that system, and in the strong-measurement limit, can theoretically freeze the free evolution completely. This is the quantum Zeno effect. We utilize quantum-nondemolition photon-counting techniques to realize the Zeno effect on the evolution of either a two-level Jaynes-Cummings atom interacting with a resonant cavity mode, or on two electromagnetic modes configured as a multilevel parametric frequency converter. These systems interact with another electromagnetic cavity mode via a quadratic coupling system based on four-wave mixing and constructed so as to be a nondemolition measurement of the photon number. This mode is then coupled to the environment through the cavity mirrors. This measurement is shown to be a measurement of system populations, which generates the desired Zeno effect and in the strong-measurement limit will freeze the free dynamics of the system.