Abstract
Number-resolving single-photon detectors represent a key technology for a host of quantum optics protocols, but despite significant efforts, state-of-the-art devices are limited to few photons. In contrast, state-dependent atom counting in arrays can be done with extremely high fidelity up to hundreds of atoms. We show that in waveguide QED, the problem of photon counting can be reduced to atom counting, by entangling the photonic state with an atomic array in the collective number basis. This is possible as the incoming photons couple to collective atomic states and can be achieved by engineering a second decay channel of an excited atom to a metastable state. Our scheme is robust to disorder and finite Purcell factors, and its fidelity increases with atom number. Analyzing the state of the re-emitted photons, we further show that if the initial atomic state is a symmetric Dicke state, dissipation engineering can be used to implement a nondestructive photon-number measurement, in which the incident state is scattered into the waveguide unchanged. Our results generalize to related platforms, including superconducting qubits.
Highlights
Single-photon detectors have a long history, with a plethora of technologies available [1]
We extend these concepts to a quantum nondemolition (QND) measurement in Sec
We have explored the use of arrays of quantum emitters coupled to waveguides for number-resolving photon detection
Summary
Single-photon detectors have a long history, with a plethora of technologies available [1]. This can be achieved either through continuous measurement, for example through dispersive coupling [14,15,16,17,18,19], or if the detector permanently changes its state and is read out later, as in impedancematched -systems [20,21,22,23,24,25,26]. The key idea here is to engineer atoms such that for each incident photon in the waveguide, exactly one atom changes its internal state, such that a subsequent measurement of the atomic state yields the number of photons in the scattered wave packet We do this by identifying conditions such that all photons are absorbed in one atomic transition (g → e, blue in Fig. 1) and dissipated in a different one (e → s, green).
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have