Second-order coherence of microwave photons emitted by a quantum point contact

Abstract

Shot-noise of electrons that are transmitted with probability $T$ through a quantum point contact (biased at a voltage $V_0$) leads to a fluctuating current that in turn emits radiation in the microwave regime. By calculating the Fano factor $F$ for the case where only a single channel contributes to the transport, it has been shown that the radiation produced at finite frequency ${\omega }_0$ close to $e{V}_0/\hslash$ and at low temperatures is nonclassical with sub-Poissonian statistics ($F<1$). The origin of this effect is the fermionic nature of the electrons producing the radiation, which reduces the probability of simultaneous emission of two or more photons. However, the Fano factor, being a time-averaged quantity, offers only limited information about the system. Here, we calculate the second-order coherence $g^{(2)}(\tau )$ for this source of radiation. We show that due to the interference of two contributions, two photon processes (leading to bunching) are completely absent at zero temperature for $T=50\%$. At low temperatures, we find a competition of the contribution due to Gaussian current-current fluctuations (leading to bunching) with the one due to non-Gaussian fluctuations (leading to antibunching). At slightly elevated temperatures, the non-Gaussian contribution becomes suppressed whereas the Gaussian contributions remain largely independent of temperature. We show that the competition of the two contributions leads to a nonmonotonic behavior of the second-order coherence as a function of time. As a result, $g^{(2)}(\tau )$ obtains a minimal value for times ${\tau }^{\ast }\simeq {\omega }_0^{-1}$. Close to this time, the second-order coherence remains below 1 at temperatures where the Fano factor is already above 1. We identify realistic experimental parameters that can be used to test the sub-Poissonian nature of the radiation.

9 pages, 7 figures

References in corpus (6)

• Experimental Test of the High-Frequency Quantum Shot Noise Theory in a Quantum Point Contact
• Wave-packet Formalism of Full Counting Statistics
• Antibunched photons emitted by a quantum point contact out of equilibrium
• Bunching and anti-bunching in electronic transport
• Tunable microwave impedance matching to a high impedance source using a Josephson metamaterial
• Nonzero temperature effects on antibunched photons emitted by a quantum point contact out of equilibrium

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• Quantum Properties of the radiation emitted by a conductor in the Coulomb Blockade Regime
• Statistics of radiation due to non-degenerate Josephson parametric down conversion
• Inelastic scattering of microwave radiation in the dynamical Coulomb blockade
• Charge-photon transport statistics and short-time correlations in a single quantum dot-resonator system with arbitrarily large coupling parameter
• Superbunched radiation of a tunnel junction due to charge quantization