Strongly driving a two-level quantum system with light leads to a ladder of Floquet states separated by the photon energy. Nanoscale quantum devices allow the interplay of confined electrons, phonons, and photons to be studied under strong driving conditions. Here we show that a single electron in a periodically driven DQD functions as a "Floquet gain medium," where population imbalances in the DQD Floquet quasi-energy levels lead to an intricate pattern of gain and loss features in the cavity response. We further measure a large intra-cavity photon number n_c in the absence of a cavity drive field, due to equilibration in the Floquet picture. Our device operates in the absence of a dc current -- one and the same electron is repeatedly driven to the excited state to generate population inversion. These results pave the way to future studies of non-classical light and thermalization of driven quantum systems.

1 aStehlik, J.1 aLiu, Y.-Y.1 aEichler, C.1 aHartke, T., R.1 aMi, X.1 aGullans, Michael1 aTaylor, J., M.1 aPetta, J., R. uhttp://journals.aps.org/prx/abstract/10.1103/PhysRevX.6.04102701372nas a2200181 4500008004100000245007800041210006900119260001500188300001100203490000800214520084100222100002101063700001601084700001701100700001801117700001901135856003601154 2016 eng d00aSisyphus Thermalization of Photons in a Cavity-Coupled Double Quantum Dot0 aSisyphus Thermalization of Photons in a CavityCoupled Double Qua c2016/07/25 a0568010 v1173 aA strongly driven quantum system, coupled to a thermalizing bath, generically evolves into a highly non-thermal state as the external drive competes with the equilibrating force of the bath. We demonstrate a notable exception to this picture for a microwave resonator interacting with a periodically driven double quantum dot (DQD). In the limit of strong driving and long times, we show that the resonator field can be driven into a thermal state with a chemical potential given by a harmonic of the drive frequency. Such tunable chemical potentials are achievable with current devices and would have broad utility for quantum simulation in circuit quantum electrodynamics. As an example, we show how several DQDs embedded in an array of microwave resonators can induce a phase transition to a Bose-Einstein condensate of light.

1 aGullans, Michael1 aStehlik, J.1 aLiu, Y., -Y.1 aPetta, J., R.1 aTaylor, J., M. uhttp://arxiv.org/abs/1512.0124801515nas a2200181 4500008004100000245007100041210006900112260001500181300001100196490000700207520099200214100001701206700001601223700002101239700001901260700001801279856003601297 2015 eng d00aInjection Locking of a Semiconductor Double Quantum Dot Micromaser0 aInjection Locking of a Semiconductor Double Quantum Dot Micromas c2015/11/02 a0538020 v923 a Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models. 1 aLiu, Y., -Y.1 aStehlik, J.1 aGullans, Michael1 aTaylor, J., M.1 aPetta, J., R. uhttp://arxiv.org/abs/1508.0414701003nas a2200181 4500008004100000245006900041210006800110260001500178300001100193490000800204520048000212100002100692700001700713700001600730700001800746700001900764856003800783 2015 eng d00aPhonon-Assisted Gain in a Semiconductor Double Quantum Dot Maser0 aPhononAssisted Gain in a Semiconductor Double Quantum Dot Maser c2015/05/13 a1968020 v1143 aWe develop a microscopic model for the recently demonstrated double quantum dot (DQD) maser. In characterizing the gain of this device we find that, in addition to the direct stimulated emission of photons, there is a large contribution from the simultaneous emission of a photon and a phonon, i.e., the phonon sideband. We show that this phonon-assisted gain typically dominates the overall gain which leads to masing. Recent experimental data are well fit with our model. 1 aGullans, Michael1 aLiu, Y., -Y.1 aStehlik, J.1 aPetta, J., R.1 aTaylor, J., M. uhttp://arxiv.org/abs/1501.03499v301150nas a2200193 4500008004100000245004800041210004800089260001500137300001400152490000800166520063700174100001700811700001600828700001600844700002100860700001900881700001800900856003800918 2015 eng d00aSemiconductor double quantum dot micromaser0 aSemiconductor double quantum dot micromaser c2015/01/15 a285 - 2870 v3473 a The coherent generation of light, from masers to lasers, relies upon the specific structure of the individual emitters that lead to gain. Devices operating as lasers in the few-emitter limit provide opportunities for understanding quantum coherent phenomena, from THz sources to quantum communication. Here we demonstrate a maser that is driven by single electron tunneling events. Semiconductor double quantum dots (DQDs) serve as a gain medium and are placed inside of a high quality factor microwave cavity. We verify maser action by comparing the statistics of the emitted microwave field above and below the maser threshold. 1 aLiu, Y., -Y.1 aStehlik, J.1 aEichler, C.1 aGullans, Michael1 aTaylor, J., M.1 aPetta, J., R. uhttp://arxiv.org/abs/1507.06359v1