Yaakov Shaked

Classical-to-Quantum Transition with Broadband Four-Wave Mixing

A key question of quantum optics is how nonclassical biphoton correlations at low power evolve into classical coherence at high power. Direct observation of the crossover from quantum to classical behavior is desirable, but difficult due to the lack of adequate experimental techniques that cover the ultrawide dynamic range in photon flux from the single photon regime to the classical level. We investigate biphoton correlations within the spectrum of light generated by broadband four-wave mixing over a large dynamic range of ∼80  dB in photon flux across the classical-to-quantum transition using a two-photon interference effect that distinguishes between classical and quantum behavior. We explore the quantum-classical nature of the light by observing the interference contrast dependence on internal loss and demonstrate quantum collapse and revival of the interference when the four-wave mixing gain in the fiber becomes imaginary.

Pairwise mode-locking of coupled parametric oscillators

The canonical example of coherent interaction between oscillators is a system of coupled pendulums — where due to the coupling, energy is transferred slowly from one oscillator to the other and back at a beat frequency that reflects the coupling strength. A system of coupled pendulums is an idealization of coherent transfer of energy, that cannot be directly observed in steady-state — a real system will eventually lose coherence due to dissipation and unwanted couplings to the environment. Parametric amplifiers offer a method to coherently amplify the oscillation in a way that conserves the coherent dynamics between the coupled oscillators. An optical parametric oscillator (OPO) relies on coherent amplification of light to generate coherent radiation, but the dynamics and coherence properties of an OPO are fundamentally different from those of a standard laser, the amplification mechanism in an OPO relies on a coherent parametric coupling of energy from the strong pump field (ω p ) to a pair of frequencies, signal (ω s ) and idler (ω i ) such that the energy and momentum of light are conserved (ω p = ω s + ω i , k p = + k i ). An OPO therefore always generates pairs of correlated coherent fields, conserving the beat coherence.

Ultra-broadband homodyne-detection for parallel processing of quantum-information

Quantum-optical states, such as single-photons or quadrature-squeezed light, used for processing quantum-information easily reach optical bandwidths, however homodyne-detection — a major quantum-information tool, is sub-GHz limited. Using optical parametric-amplification we demonstrate effectively bandwidth unlimited optical-homodyne measurement.

Pairwise Mode-Locking of Coupled Parametric Oscillators

The canonical example of coherent interaction between oscillators is a system of coupled pendulums — where due to the coupling, energy is transferred slowly from one oscillator to the other and back at a beat frequency that reflects the coupling strength. A system of coupled pendulums is an idealization of coherent transfer of energy, that cannot be directly observed in steady-state — a real system will eventually lose coherence due to dissipation and unwanted couplings to the environment. Parametric amplifiers offer a method to coherently amplify the oscillation in a way that conserves the coherent dynamics between the coupled oscillators. An optical parametric oscillator (OPO) relies on coherent amplification of light to generate coherent radiation, but the dynamics and coherence properties of an OPO are fundamentally different from those of a standard laser, the amplification mechanism in an OPO relies on a coherent parametric coupling of energy from the strong pump field (ω<inf>p</inf>) to a pair of frequencies, signal (ω<inf>s</inf>) and idler (ω<inf>i</inf>) such that the energy and momentum of light are conserved (ω<inf>p</inf> = ω<inf>s</inf> + ω<inf>i</inf>, k<inf>p</inf> = + k<inf>i</inf>). An OPO therefore always generates pairs of correlated coherent fields, conserving the beat coherence.

Demonstration of the Quantum Response to Loss with Ultra-Broadband Bi-Photons Interference

By using an ultra-broad (100THz) bi-photon source and a pairwise interferometer, we measure the bi-photons spectral phase and amplitude, and demonstrate the quantum dependence of the interference contrast on internal loss.

Complete Measurement of the Two-Photon Wave Function using High Contrast Quantum Interference

Exploiting quantum pairwise interference, we measure the spectral phase of ultra broadband entangled photon pairs. The nonclassical nature of the interference is manifested by observing the reduction of fringe contrast as linear loss is introduced.