Measuring the quantum nature of light with a single source and a single detector

Abstract

An elementary experiment in optics consists of a light source and a detector. Yet, if the source generates nonclassical correlations such an experiment is capable of unambiguously demonstrating the quantum nature of light. We realized such an experiment with a defect center in diamond and a superconducting detector. Previous experiments relied on more complex setups, such as the Hanbury Brown and Twiss configuration, where a beam splitter directs light to two photodetectors, creating the false impression that the beam splitter is a fundamentally required element. As an additional benefit, our results provide a simplification of the widely used photon-correlation techniques. Loudon [4] that a much simpler experiment in which the light is arranged to fall on a single phototube would be sufficient. Here, we perform such an experiment and show single-photon statistics from a quantum emitter with only one detector. The superconducting detector we fabricated has a dead time shorter than the coherence time of the emitter. No beam splitter is employed, yet anticorrelations are observed. Our work simplifies a widely used photon-correlation technique [5,6].A single-photon Fock state is a single excitation of a mode k of the electromagnetic field a † k |0 . A more general single-photon state appropriate to describe the final wave packet generated by a single-photon source in an experiment is a superposition of different spatio-temporal modes containing in total one excitation. The probability P (n) of finding exactly n excitations in the modes may distinguish different states of light. Figures 1(a) and 1(b) show a schematic representation of a coherent state where P (n) is a Poissonian distribution together with a number (or Fock) state with exactly 1 photon per mode, respectively. In the case of a single-photon state (n = 1) detection of a single excitation projects the measured mode to the vacuum state; i.e., the probability of detecting another photon in the very same mode is zero. Since the temporal mode profile is associated with a characteristic coherence time τ c , coincidence events within the time interval τ c are absent; antibunching is observed. On the contrary, * steudle@physik.hu-berlin.de † http://www.physik.hu-berlin.de/nano for a coherent state the probability of detecting a photon is independent of any previous detection event. Antibunching is thus not only a consequence of photons being indivisible particles but requires a specific quantum statistical distribution of discrete excitations. The latter requirement is overlooked in a simple explanation of antibunching in a HBT experiment [ Fig. 1(c)]. There a photon is regarded as a classical indivisible particle and necessarily has to decide which path to take when impinging on a beam splitter. Such an interpretation is certainly naïve. It even led to paradoxical conclusions, such as in some implementations of Wheeler's delayed choice paradox [7].Today, many different sources have been realized that generate antibunched light such as single-photon sources ...

Nonclassical higher-order photon correlations with a quantum dot strongly coupled to a photonic-crystal nanocavity

“…It is worth noting that the use of photon-number-resolving detectors [15,16], especially transition-edge sensors [17] or superconducting nanowires [18][19][20], could provide an alternative technique for the characterization of multi-photon Fock states; however, these devices are still under experimental investigation and are not yet widely available.…”

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

“…All measurements of G (2) aa (τ ) are in good agreement with calculations 25 , both for δτ = 0 (solid lines) and for δτ = 100 ns (not shown). Here, it is interesting to note that a second-order auto-correlation function is rarely directly measured, because of the the lack of sufficiently fast single-photon detectors 27 . In contrast, using our heterodyne detection scheme we are capable of measuring G (2) aa (τ ) for multi-photon states.…”

Using defect centres in diamonds to build photonic and quantum optical devices

“…Additional bunching is observed owing to occasional population of a metastable singlet state of the NV centre. From Steudle et al (2012), © 2012, APS.…”

“…In this way, count rates of up to a few million photons per second from a single NV centre can be achieved. Sources like this were used in the experiments by Steudle et al (2012) and Jiang et al (2012) reviewed in the following subsections.…”

“…In confi guration 2, the time intervals between the signals from the two APDs, with a dead time of 30 ns, were recorded with a time interval counter. From Steudle et al (2012 as defi ned in Section 7.2 in two different confi gurations, as shown in Fig. 7.14 (b), namely a single-detector set-up with an SSPD (confi guration 1) and a standard HBT set-up with two commercial avalanche photodiodes (confi guration 2).…”