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The Rochester Conferences on Coherence and Quantum Optics and the Quantum Information and Measurement meeting

Single Photon Nonlinearities and Macroscopic Entanglement

Rob Thew, Natalia Bruno, Thiago Guerreiro, Enrico Pomarico, Anthony Martin, Bruno Sanguinetti, Pavel Sekatski, Nicolas Sangouard, Jason S. Pelc, Carsten Langrock, M. M. Fejer, Hugo Zbinden, Nicolas Gisin

Published Jan 1, 2013• 0 citations

Abstract

I will discuss a couple of recent experiments that are at opposite extremes of quantum photonics. We have demonstrated an integrated nonlinear optics scheme – based on sum-frequency generation - capable of photon-photon interactions. This approach has the potential for significant impact in quantum communication, e.g. for heralding entanglement over large distances and providing a significant step towards device-independent quantum key distribution. It also has the added advantage that it is incredibly flexible in terms of the wavelengths and bandwidths that can be incorporated, thus providing a potential solution for a wide range of experiments and applications beyond quantum communication. In a more fundamental experiment, we have tested a way of characterising macroscopic entanglement – the approach firstly amplifies a “microscopic” - single photon - entangled state, to the level of ~500 photons, before reducing this state back to the microscopic regime where a well known entanglement witness can be used to characterise the macroscopic state.

DOI: 10.1364/qim.2013.th2b.3

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I will discuss a couple of recent experiments that are at opposite extremes of quantum photonics. We have demonstrated an integrated nonlinear optics scheme – based on sum-frequency generation - capable of photon-photon interactions. This approach has the potential for significant impact in quantum communication, e.g. for heralding entanglement over large distances and providing a significant step towards device-independent quantum key distribution. It also has the added advantage that it is incredibly flexible in terms of the wavelengths and bandwidths that can be incorporated, thus providing a potential solution for a wide range of experiments and applications beyond quantum communication. In a more fundamental experiment, we have tested a way of characterising macroscopic entanglement – the approach firstly amplifies a “microscopic” - single photon - entangled state, to the level of ~500 photons, before reducing this state back to the microscopic regime where a well known entanglement witness can be used to characterise the macroscopic state.

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Entanglement is one of the most peculiar features consequent upon quantum mechanics. It is at-tributed essentially to the nonlocal nature of quantum correlation between two or more particles. The strangeness of entanglement has been demonstrated by a number of paradoxes from the dawn of quantum mechanics: one example is that proposed by Einstein, Podolsky and Rosen [1], and its variety is famous Schrödinger’s cat. However, recent quantum technologies have reached an unprecedented stage at which we can directly manipulate and utilize the entanglement to go beyond the limit of clas-sical technologies. In fact, recent progress of quantum information and communication technologies relies on the use of entanglement [2]. As well, entanglement is applicable to ultra-high precise meas-urements, one prominent example of which is the quantum optical imaging and interferometry with ultra-high resolution that surpasses the classical diffraction limit [3]. In addition to exploring such novel applications, the methodology of generating entanglement is also indispensable to practical quantum technologies. In my talk, I will review the recent progress of such quantum technologies utilizing entanglement as well as its generation. In particular, I will focus on the recent experiments [4-7] of quantum optical interferometry with entangled photons that exhibit reduced de Broglie wave-length of photons [8]. I also mention the generation of entangled photons in a semiconductor that we

We demonstrate postselection free heralded qubit amplification for Time-Bin qubits and single photon states in an all-fibre, telecom-wavelength, scheme that highlights the simplicity, stability and potential for fully integrated photonic solutions. Exploiting high-efficiency superconducting detectors, the gain, fidelity and the performance of the amplifier are studied as a function of loss. We also demonstrate the first heralded single photon amplifier with independent sources. This provides a significant advance towards demonstrating device-independent quantum key distribution as well as fundamental tests of quantum mechanics over extended distances.