Single-Photon Distillation via a Photonic Parity Measurement Using Cavity QED

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Single-Photon Distillation via a Photonic Parity Measurement Using Cavity QED

Severin Daiss, Stephan Welte, Bastian Hacker, Lin Li, and Gerhard Rempe

Phys. Rev. Lett. 122, 133603 – Published 5 April 2019

Abstract

Single photons with tailored temporal profiles are a vital resource for future quantum networks. Here we distill them out of custom-shaped laser pulses that reflect from a single atom strongly coupled to an optical resonator. A subsequent measurement on the atom is employed to herald a successful distillation. Out of vacuum-dominated light pulses, we create single photons with fidelity 66(1)%, two-and-more-photon suppression 95.5(6)%, and a Wigner function with negative value $- 0.125 (6)$ . Our scheme applied to state-of-the-art fiber resonators could boost the single-photon fidelity to up to 96%.

Received 27 December 2018

DOI:https://doi.org/10.1103/PhysRevLett.122.133603

Physics Subject Headings (PhySH)

Atoms, ions, & molecules in cavities Cavity quantum electrodynamics Photon statistics Quantum states of light Single photon sources

Atomic, Molecular & Optical

Authors & Affiliations

Severin Daiss^*, Stephan Welte, Bastian Hacker, Lin Li^†, and Gerhard Rempe

Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany

^*severin.daiss@mpq.mpg.de
^†Present address: School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China

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Vol. 122, Iss. 13 — 5 April 2019

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Images

Figure 1
Setup of the experiment. Weak coherent pulses are sent to the atom-cavity system using a non-polarizing beam splitter (NPBS). They are reflected from the resonator followed by a state rotation (using a pair of Raman beams) and a state detection of the atom. A switch is used to change between different measurement setups. For homodyne detection, the light is mixed with a local oscillator (LO) beam and detected by two photodiodes (PDs). For coincidence measurements, the light can be sent into a Hanbury Brown–Twiss (HBT) setup, consisting of a beam splitter and two single-photon detectors (SPDs).
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Figure 2
Projecting onto Fock states with different parity. The photon-number distributions of the reflected light unconditioned on a measurement (left), with the atom detected in $| ↑ ⟩$ (center) and with the atom detected in $| ↓ ⟩$ (right) are shown. The data are corrected for losses occurring after the cavity. The average photon numbers of the initial coherent pulses are derived from the unconditioned data to be (0.35, 0.85, 1.48, 2.61) in (a)–(d). The bars outlined in black indicate the distribution from a calculation with our experimental parameters as discussed in Ref. [29]. The Poisson distribution for a coherent state with mean photon number according to the reflected light intensity is shown as a black line.
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Figure 3
Projection probability and fidelity with a single photon for different incoming intensities $α^{2}$ . (a) Heralding probability $P (↑)$ to detect the atom in $| ↑ ⟩$ . (b) The measured single-photon fidelity $F_{1}$ of the distilled light is shown as blue data points. The solid line is given by a calculation of our experiment with parameters as described in Ref. [29]. For comparison, the overlap of an undistilled coherent state with a single photon is displayed as a dashed red line.
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Figure 4
Single-photon Wigner function. The plot shows the reconstructed Wigner function of the produced single-photon state for an incoming coherent state with $α^{2} = 0.31$ . The two field quadratures spanning phase space are labeled $p$ and $q$ . The data are corrected for propagation and detection losses of 25.1%.
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Figure 5
Second-order correlation function. The measured data points show $g^{(2)} (0)$ of the light after a heralding state-detection event as a function of the incoming intensity $α^{2}$ . The solid line is a calculation of the expected $g^{(2)} (0)$ for our system including dark counts of the SPDs (see Ref. [29] for details). In the inset of the figure, $g^{(2)} (τ)$ for $α^{2} = 0.11$ is displayed.
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