Time-resolved two-photon quantum interference

Legero, Thomas; Wilk, Tatjana; Kuhn, Axel; Rempe, Gerhard

doi:10.1007/s00340-003-1337-x

Cited by 173 publications

(217 citation statements)

References 17 publications

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“…For δτ = 50 ns the correlation function G (2) ab (τ ) remains close to zero at τ = 0, indicating the coalescence of those photons detected with a vanishingly small time difference 6,25,26 (see Fig. 2d).…”

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confidence: 89%

Correlations, indistinguishability and entanglement in Hong–Ou–Mandel experiments at microwave frequencies

et al. 2013

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When two indistinguishable single photons impinge at the two inputs of a beam splitter they coalesce into a pair of photons appearing in either one of its two outputs. This effect is due to the bosonic nature of photons and was first experimentally observed by Hong, Ou and Mandel 1 . Here, we present the observation of the Hong-Ou-Mandel effect with two independent single-photon sources in the microwave frequency domain. We probe the indistinguishability of single photons, created with a controllable delay, in time-resolved secondorder cross-and auto-correlation function measurements. Using quadrature amplitude detection we are able to resolve different photon numbers and detect coherence in and between the output arms. This scheme allows us to fully characterize the two-mode entanglement of the spatially separated beam-splitter output modes. Our experiments constitute a first step towards using two-photon interference at microwave frequencies for quantum communication and information processing 2-5 .So far, Hong-Ou-Mandel (HOM) two-photon interference has been demonstrated exclusively using photons at optical or telecom wavelengths. Experiments were performed with photons emitted from a single source using parametric downconversion 1 , trapped ions 3 , atoms 6 , quantum dots 7 and single molecules 8 . The HOM effect has also been observed with two independent sources 9-15 realizing indistinguishable single-photon states, which are required as a resource in quantum networks or linear-optics quantum computation. Such experiments have also been performed using donor impurities as sources 16 including nitrogen-vacancy centres in diamond (see ref. 17 and references therein). Furthermore, the HOM effect has been employed to create entanglement between ions 18 in spatially separated traps, and to realize a controlled-NOT gate in a small-scale photonic network 19 . Similar physics is also actively explored with ballistic electrons in solids (see ref. 20 and references therein).Here, we demonstrate the HOM interference of two indistinguishable microwave photons emitted from independent triggered sources realized in superconducting circuits (see Methods). The photons are prepared in two separate microwave resonators A (B) using transmon-type qubits and decay exponentially at rates κ/2π = 4.1 (4.6) MHz through their strongly coupled output ports into the input modesâ andb of the beam splitter (see Fig. 1). The two photons then interfere at the beam splitter and are emitted into the output modesâ andb (see Fig. 1a). Using the dispersive interaction between qubit and resonator, we tune the emission frequencies of the two sources to an identical value of ν r = 7.2506 GHz. For our experiments, we sequentially create 20 single photons in each source at a rate 1/t r = 1/512 ns ∼ 1.95 MHz in a sequence repeated every 12.5 µs.To probe the photon statistics in the beam-splitter output modesâ andb we use two spatially separated heterodyne detection channels 21,22 (see dashed rectangle in Fig. 1b). Each channel consists of a set of...

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confidence: 89%

Correlations, indistinguishability and entanglement in Hong–Ou–Mandel experiments at microwave frequencies

et al. 2013

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“…Decoherence is represented by random fluctuations of the phase ϕ j as a function of time t j , such that e i½ϕ j ðtj Þ -ϕ j ðtj þΔÞ ¼ e -9Δ9=T j , where T j is the coherence time of photon j. 31,32 For the laser input state with polarisation defined by real parameters a and b, we have…”

Section: Error Analysismentioning

confidence: 99%

An entangled-LED-driven quantum relay over 1 km

et al. 2016

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Quantum cryptography allows confidential information to be communicated between two parties, with secrecy guaranteed by the laws of nature alone. However, upholding guaranteed secrecy over networks poses a further challenge, as classical receive-andresend routing nodes can only be used conditional of trust by the communicating parties, which arguably diminishes the value of the underlying quantum cryptography. Quantum relays offer a potential solution by teleporting qubits from a sender to a receiver, without demanding additional trust from end users. Here we demonstrate the operation of a quantum relay over 1 km of optical fibre, which teleports a sequence of photonic quantum bits to a receiver by utilising entangled photons emitted by a semiconductor light-emitting diode. The average relay fidelity of the link is 0.90 ± 0.03, exceeding the classical bound of 0.75 for the set of states used, and sufficiently high to allow error correction. The fundamentally low multiphoton emission statistics and the integration potential of the source present an appealing platform for future quantum networks. INTRODUCTIONQuantum key distribution 1,2 systems based on weak-coherent optical pulses have been reported that allow unique cryptographic keys to be shared between directly connected users on point-to-point 3-5 or point-to-multipoint links 6 . To establish fully quantum multipartite networks, that avoid trusting intermediate parties, 7 it is necessary to route quantum signals through a backbone of quantum nodes. 8 This can be achieved by leveraging quantum entanglement to set-up non-local correlations between measurements by end users. Examples of such schemes are distribution of entangled photon pairs to end users, where local measurements are performed, 9 or conversely, where photons are sent by two users to be projected into a Bell state by an intermediate quantum node. 10-12 Photonic quantum repeaters 13 and relays 8 use both of these effects to teleport entangled or single qubits, respectively, in a manner that can be chained to create a fully quantum network for which theoretically proven quantum security can be preserved.Here we report operation of a quantum relay over 1 km of optical fibre using entangled photons generated by a lightemitting diode to teleport photonic qubits encoded on weak coherent pulses emitted by a laser. Compared with previously reported quantum relays 14 and photonic teleportation over significant distances, 15,16 our system is directly electrically driven using a simple semiconductor device, offering a route to largescale network deployments. Teleporting weak coherent states offers potential enhancements to state-of-the art quantum key distribution systems, as it creates output photons with sub-Poissonian statistics immune to the photon number-splitting attack, 17,18 and protects against intrusions. 19

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“…Therefore, the temporal effects cannot be neglected any more when detecting pulses and the time delay τ between detected pulses at two separate detectors has to taken into account. Experiments investigating interference for such pulses with different frequencies have already been performed 14,15 . We restrict our description of the single-photon wave packets in the spacetime domain to one-mode fields with electric field operators: E (+) a (t) = α(t) a and E (+) b (t) = β(t) b.…”

Section: Hong-ou-mandel Time-resolved Interferencementioning

confidence: 99%

Witnessing Entanglement of Epr States With Second-Order Interference

Stobińska

Wódkiewicz

2006

Int. J. Mod. Phys. B

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The separability of the continuous-variable EPR state can be tested with Hanbury-Brown and Twiss type interference. The second-order visibility of such interference can provide an experimental test of entanglement. It is shown that time-resolved interference leads to the Hong, Ou and Mandel deep, that provides a signature of quantum non-separability for pure and mixed EPR states. A Hanbury-Brown and Twiss type witness operator can be constructed to test the quantum nature of the EPR entanglement.

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Time-resolved two-photon quantum interference

Cited by 173 publications

References 17 publications

Correlations, indistinguishability and entanglement in Hong–Ou–Mandel experiments at microwave frequencies

Correlations, indistinguishability and entanglement in Hong–Ou–Mandel experiments at microwave frequencies

An entangled-LED-driven quantum relay over 1 km

Witnessing Entanglement of Epr States With Second-Order Interference

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