Search

We describe an experiment in which one member of a polarization-entangled photon pair is stored in an active "loop and switch" type quantum memory device, while the other propagates through a passive optical delay line. A comparison of Bell's inequality tests performed before and after the storage is used to investigate the ability of the memory to maintain entanglement, and demonstrate a rudimentary entanglement distribution protocol. The entangled photons are produced by a conventional Spontaneous Parametric Down Conversion source with center wavelengths at 780 nm and bandwidths of $\sim$10 THz, while the memory has an even wider operational bandwidth that is enabled by the weakly dispersive nature of the Pockels effect used for polarization-insensitive switching in the loop-based quantum memory platform., Comment: 6 pages, 4 figures

Zero-photon subtraction (ZPS) is a conditional measurement process that can reduce the mean photon number of quantum optical states without physically removing any photons. Here we show that ZPS can also be used to transform certain super-Poissonian states into sub-Poissonian states, and vice versa. Combined with a well-known "no-go" theorem on conditional measurements, this effect leads to a new set of non-classicality criteria that can be experimentally tested through ZPS measurements., Comment: 7 pages, 6 figures

The process of single-photon subtraction (SPS) is known to dramatically alter the properties of certain quantum optical states. Somewhat surprisingly, subtracting zero photons can also modify quantum states and has practical applications in quantum communication. Here we experimentally investigate zero-photon subtraction (ZPS) using a wide variety of input states and conditional measurements based on actively detecting zero photons in one output port of a variable beamsplitter. We find that SPS and ZPS can exhibit complementary behavior depending on the photon statistics of the input states, and highlight deeper connections with Mandel's $Q$-parameter for classifying quantum states., Comment: 7 pages, 4 figures

Attenuating a quantum state using a beam splitter will introduce noise and decoherence. Here we show that heralding techniques can be used to attenuate Schr\"odinger cat states and squeezed vacuum states without any noise or decoherence [Mi\v{c}uda et al., Phys. Rev. Lett. 109, 180503 (2012)]. Noiseless attenuation also preserves quantum interference effects in nonclassical states such as squeezed vacuum states., Comment: 11 pages, 12 figures

Although heralding signals in quantum optics experiments are typically based on the detection of exactly one photon, it has recently been theoretically shown that heralding based on the detection of zero photons can be useful in a number of quantum information applications. Here we describe an experimental technique for "heralding on zero photons" using conventional single-photon detectors and time-tagging methods. We find that detector efficiency and dark count rates play a counterintuitive role in the ability to accurately detect zero photons, and demonstrate these effects in an experiment that involves heralding on zero photons in the well-known Hong-Ou-Mandel interferometer., Comment: 9 pages, 7 figures