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Register a new userMicrowave detection of electron-phonon interactions in a cavity-coupled double quantum dot
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Quantum confinement leads to the formation of discrete electronic states in quantum dots. Here we probe electron-phonon interactions in a suspended InAs nanowire double quantum dot (DQD) that is electric-dipole coupled to a microwave cavity. We apply a finite bias across the wire to drive a steady state population in the DQD excited state, enabling a direct measurement of the electron-phonon coupling strength at the DQD transition energy. The amplitude and phase response of the cavity field exhibit features that are periodic in the DQD energy level detuning due to the phonon modes of the nanowire. The observed cavity phase shift is consistent with theory that predicts a renormalization of the cavity center frequency by coupling to phonons.
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We investigate the non-classical states of light that emerge in a microwave resonator coupled to a periodically-driven electron in a nanowire double quantum dot (DQD). Under certain drive configurations, we find that the resonator approaches a thermal state at the temperature of the surrounding substrate with a chemical potential given by a harmonic of the drive frequency. Away from these thermal regions we find regions of gain and loss, where the system can lase, or regions where the DQD acts as a single-photon source. These effects are observable in current devices and have broad utility for quantum optics with microwave photons.
We investigate spin states of few electrons in a double quantum dot by coupling them weakly to a magnetic field resilient NbTiN microwave resonator. We observe a reduced resonator transmission if resonator photons and spin singlet states interact. This response vanishes in a magnetic field once the quantum dot ground state changes from a spin singlet into a spin triplet state. Based on this observation, we map the two-electron singlet-triplet crossover by resonant spectroscopy. By measuring the resonator only, we observe Pauli spin blockade known from transport experiments at finite source-drain bias and detect an unconventional spin blockade triggered by the absorption of resonator photons.
We investigate the influence of electron-phonon interactions on the dynamical properties of a quantum-dot-cavity QED system. We show that non-Markovian effects in the phonon reservoir lead to strong changes in the dynamics, arising from photon-assisted dephasing processes, not present in Markovian treatments. A pronounced consequence is the emergence of a phonon induced spectral asymmetry when detuning the cavity from the quantum-dot resonance. The asymmetry can only be explained when considering the polaritonic quasi-particle nature of the quantum-dot-cavity system. Furthermore, a temperature induced reduction of the light-matter coupling strength is found to be relevant in interpreting experimental data, especially in the strong coupling regime.
Single photon detectors are key for time-correlated photon counting applications [1] and enable a host of emerging optical quantum information technologies [2]. So far, the leading approach for continuous and efficient single-photon detection in the optical domain has been based on semiconductor photodiodes [3]. However, there is a paucity of efficient and continuous single-photon detectors in the microwave regime, because photon energies are four to five orders of magnitude lower therein and conventional photodiodes do not have that sensitivity. Here we tackle this gap and demonstrate how itinerant microwave photons can be efficiently and continuously converted to electrical current in a high-quality, semiconducting nanowire double quantum dot that is resonantly coupled to a cavity. In particular, in our detection scheme, an absorbed photon gives rise to a single electron tunneling event through the double dot, with a conversion efficiency reaching 6 %. Our results pave the way for photodiodes with single-shot microwave photon detection, at the theoretically predicted unit efficiency [4].
We demonstrate a method of tuning a semiconductor quantum dot (QD) onto resonance with a cavity mode all-optically. We use a system comprised of two evanescently coupled cavities containing a single QD. One resonance of the coupled cavity system is used to generate a cavity enhanced optical Stark shift, enabling the QD to be resonantly tuned to the other cavity mode. A twenty-seven fold increase in photon emission from the QD is measured when the off-resonant QD is Stark shifted into the cavity mode resonance, which is attributed to radiative enhancement of the QD. A maximum tuning of 0.06 nm is achieved for the QD at an incident power of 88 {mu}W.
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