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Implementing a single-photon quantum nondemolition device with only linear optics and projective measurements

Pieter Kok, Hwang Lee, Jonathan P. Dowling

Published Feb 7, 2002• 1 citation
OpenAlex

Abstract

In this Letter we describe an optical interferometer that signals the presence of a single photon in a particular input state (c0 |0> + c1 |1> + c2 |2>) without destroying it. The interferometer employs two auxiliary single-photon sources and three detectors. The ideal efficiency of this quantum nondemolition (QND) device is 1/7. Furthermore, the interferometer presented is in principle not bound to a specific frequency range.

Related papers

Single-photon quantum-nondemolition detectors constructed with linear optics and projective measurements

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arXiv:quant-ph/0210096•Physical Review A•Dec 26, 2002•13 citations
In this Letter we describe an optical interferometer that signals the presence of a single photon in a particular input state (c0 |0> + c1 |1> + c2 |2>) without destroying it. The interferometer employs two auxiliary single-photon sources and three detectors. The ideal efficiency of this quantum nondemolition (QND) device is 1/7. Furthermore, the interferometer presented is in principle not bound to a specific frequency range.
Optical quantum-nondemolition devices can provide essential tools for quantum information processing. Here, we describe several optical interferometers that signal the presence of a single photon in a particular input state without destroying it. We discuss both entanglement-assisted and nonentanglement-assisted interferometers, with ideal and realistic detectors. We found that the existing detectors with 88% quantum efficiency and single-photon resolution can yield output fidelities of up to 89%, depending on the input state. Furthermore, we construct expanded protocols to perform quantum-nondemolition detections of single photons that leave the polarization invariant. For detectors with 88% efficiency, we found polarization-preserving output fidelities of up to 98.5%.
Two interferometric quantum-nondemolition (QND) devices have been proposed: (1) a polarization-independent device and (2) a polarization-preserving device. The prolarization-independent device works on an input state of up to two photons, whereas the polarization-preserving device works on a superposition of vacuum and single- photon states. The overall function of the device would be to probabilistically generate a unique detector output only when its input electromagnetic mode was populated by a single photon, in which case its output mode would also be populated by a single photon. Like other QND devices, the proposed devices are potentially useful for a variety of applications, including such areas of NASA interest as quantum computing, quantum communication, detection of gravity waves, as well as pedagogical demonstrations of the quantum nature of light. Many protocols in quantum computation and quantum communication require the possibility of detecting a photon without destroying it. The only prior single- photon-detecting QND device is based on quantum electrodynamics in a resonant cavity and, as such, it depends on the photon frequency. Moreover, the prior device can distinguish only between one photon and no photon. The proposed interferometric QND devices would not depend on frequency and could distinguish between (a) one photon and (b) zero or two photons. The first proposed device is depicted schematically in Figure 1. The input electromagnetic mode would be a superposition of a zero-, a one-, and a two-photon quantum state. The overall function of the device would be to probabilistically generate a unique detector output only when its input electromagnetic mode was populated by a single photon, in which case its output mode also would be populated by a single photon.
In this paper, we propose a resource-optimal linear-optical scheme for quantum nondemolition detection of single-photon presence. By measuring the state of ancillary photons, the presence of a photon in signal mode is revealed with a success probability of 1/2 without any disturbance to its state. We also show how to tune the setup to perform quantum nondemolition measurement of the signal photon state, and we provide a tradeoff between the extracted information and the signal state disturbance. Moreover, the optimality of resources and methods by which to increase the success probability are discussed.
Measuring the polarization of a single photon typically results in its destruction. We propose, demonstrate, and completely characterize a quantum nondemolition (QND) scheme for realizing such a measurement nondestructively. This scheme uses only linear optics and photodetection of ancillary modes to induce a strong nonlinearity at the single-photon level, nondeterministically. We vary this QND measurement continuously into the weak regime and use it to perform a nondestructive test of complementarity in quantum mechanics. Our scheme realizes the most advanced general measurement of a qubit to date: it is nondestructive, can be made in any basis, and with arbitrary strength.
We propose a scheme to implement a single-mode quantum filter, which selectively eliminates the one-photon state in a quantum state $\ensuremath{\alpha}|0〉+\ensuremath{\beta}|1〉+\ensuremath{\gamma}|2〉.$ The vacuum state and the two-photon state are transmitted without any change. This scheme requires single-photon sources, linear optical elements, and photon detectors. Furthermore, we demonstrate how this filter can be used to realize a two-qubit projective measurement and to generate multiphoton polarization entangled states.