Mode-resolved photon counting via cascaded quantum frequency conversion

Abstract

Resources for the manipulation and measurements of high-dimensional photonic signals are crucial for implementing qudit-based applications. Here we propose potentially high-performance, chip-compatible devices for such purposes by exploiting quantum-frequency conversion in nonlinear optical media. Specifically, by using sum-frequency generation in a χ (2) waveguide we show how mode-resolved photon counting can be accomplished for telecom-band photonic signals subtending multiple temporal modes. Our method is generally applicable to any nonlinear medium with arbitrary dispersion property. c 2013 Optical Society of America OCIS codes: 190.4410, 270.5290 Photonic signals are widely employed in many modern applications such as secure key generation, quantum computation, and near Holevo-capacity telecommunications [1]. In these applications, photons occupying low-dimensional Hilbert spaces composed of polarization or spatial degrees of freedom are most commonly used. Recently, the use of high-dimensional photonic signals, known as qud its, has attracted attention as they can offer significant advantages over qubits in terms of higher channel capacity, better information security, and so on. There have been quite a few proposals for using photonic qudits in applications such as secure telecommunications [2] and super-dense coding [3].Crucial to implementing the aforementioned quditbased applications are the capabilities for manipulating and measuring high-dimensional photonic signals. Existing solutions have been based on serializing multiple, linear, two-port optical devices [4] or using lossy spatialmode modulators [5]. Their performance in practice, particularly in large-d systems, will be highly inefficient due to the need for complicated experimental setups with high concomitant transmission losses.In this Letter, we study a potentially high efficiency, low-loss approach for manipulating and measuring photonic signals in high-dimensional Hilbert spaces composed of polarization, spatial, and temporal degrees of freedom. It is built on quantum-frequency conversion (QFC), a coherent process that can translate the carrier frequency (wavelength) of photonic signals without disturbing their quantum states, including any correlation or entanglement with other quantum objects [6]. It is well known that QFC in nonlinear media is efficient only for those appropriate combinations of wavelengths, spatiotemporal modes, and polarizations of the interacting light waves for which phase matching (PM) occurs. Thus it is possible to engineer the conditions for PM such that only photons in desired modes are frequency converted with high efficiency, while those in other modes remain unaffected [7]. By detecting the frequency-converted signals with ordinary single-photon detectors, differences in the photons' mode-profile details, which are otherwise difficult to monitor, can be precisely measured. In addition, by using photon-numberresolving (PNR) detectors, mode-resolved photon counting (MRPC) can be accomplished, based on which...

Temporal mode selectivity by frequency conversion in second-order nonlinear optical waveguides

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Photon Temporal Modes: A Complete Framework for Quantum Information Science

“…[46][47][48], which forego group-velocity matching. Although potentially simpler from an experimental point of view, these approaches cannot generally reach high selectivities as defined above [43].…”

Upconversion-based receivers for quantum hacking-resistant quantum key distribution

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