ABSTRACT
Optical N00N states are N-photon path entangled states with important applications in quantum metrology. However, their use was limited till now owing to the difficulties of generating them in an efficient and robust manner. Here we propose and experimentally demonstrate two new simple, compact and robust schemes to generate path entangled N00N states with N = 2 that emerge directly from the nonlinear interaction. The first scheme is based on shaping the pump beam, and the second scheme is based on modulating the nonlinear coefficient of the crystal. These new methods exhibit high coincidence count rates for the detection of a N00N state, reaching record value of 2 × 105 coincidences per second. We observe super-resolution by measuring the second order correlation on the generated N = 2 state in an interferometric setup, showing the distinct fringe periodicity at half of the optical wavelength. Our findings may pave the way towards scalable and efficient sources for super-resolved quantum metrology applications and for the generation of bright squeezed vacuum states.
ABSTRACT
We present a technique that improves the signal-to-noise-ratio (SNR) of range-finding, sensing, and other light-detection applications. The technique filters out low photon numbers using photon-number-resolving detectors. This technique has no classical analog and cannot be done with classical detectors. We investigate the properties of our technique and show under what conditions the scheme surpasses the classical SNR. Finally, we simulate the operation of a rangefinder, showing improvement with a low number of signal samplings and confirming the theory with a high number of signal samplings.
ABSTRACT
One of the most important challenges in modern quantum optical applications is the demonstration of efficient, scalable, on-chip single photon sources, which can operate at room temperature. In this paper we demonstrate a room-temperature single photon source based on a single colloidal nanocrystal quantum dot positioned inside a circular bulls-eye shaped hybrid metal-dielectric nanoantenna. Experimental results show that 20% of the photons are emitted into a very low numerical aperture (NA < 0.25), a 20-fold improvement over a free-standing quantum dot, and with a probability of more than 70% for a single photon emission. With an NA = 0.65 more than 35% of the single photon emission is collected. The single photon purity is limited only by emission from the metal, an obstacle that can be bypassed with careful design and fabrication. The concept presented here can be extended to many other types of quantum emitters. Such a device paves a promising route for a high purity, high efficiency, on-chip single photon source operating at room temperature.
ABSTRACT
We demonstrate an isotropic depolarizing channel with a controllable degree of depolarization. The depolarizer is composed of four birefringent crystals and half-wave plates. Quantum process tomography results of the depolarization effect on single photons agree well with the theoretical prediction. This depolarizer can be used to test quantum communication protocols with photons.
ABSTRACT
We show that during the spatiotemporal compression in a periodic Kerr waveguide array, stimulated Raman scattering can effectively balance the effects of self-phase modulation, diffraction, and group-velocity dispersion, eliminating collapse and breakup over a wide range of input powers and leading to stable propagation in a single site.
