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arXiv:1501.02111 · Physical Review B

Probing charge fluctuator correlations using quantum dot pairs

Vishwas S. Purohit, Bernd Braunecker, Brendon W. Lovett

Published Jun 1, 2015• 0 citations
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Abstract

We study a pair of quantum dot exciton qubits interacting with a number of fluctuating charges that can induce a Stark shift of both exciton transition energies. We do this by solving the optical master equation using a numerical transfer matrix method. We find that the collective influence of the charge environment on the dots can be detected by measuring the correlation between the photons emitted when each dot is driven independently. Qubits in a common charge environment display photon bunching, if both dots are driven on resonance or if the driving laser detunings have the same sense for both qubits, and antibunching if the laser detunings have opposite signs. We also show that it is possible to detect several charges fluctuating at different rates using this technique. Our findings expand the possibility of measuring qubit dynamics in order to investigate the fundamental physics of the environmental noise that causes decoherence.

DOI
10.1103/physrevb.91.245301

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We report a comprehensive investigation of carrier-transfer dynamics in a single InAs quantum dot (QD) based on second-order photon correlation measurements. The experimentally obtained auto and crosscorrelation functions as well as photoluminescence intensities are successfully explained on the basis of a series of rate equations with common excitation and also single-carrier-capture/escape rates to/from a QD. This approach enables us to understand the carrier-transfer dynamics responsible for the stability of a quantum two-level system formed in a single QD under various excitation conditions. We clarify that the transition between neutral and charged excitonic states is suppressed by one order of magnitude under quasiresonant excitation.
Abstract. The coherent time evolution of electrons in double quantum dots induced by fast bias-voltage switches is studied theoretically. As it was shown experimentally, such driven double quantum dots are potential devices for controlled manipulation of charge qubits. By numerically solving a quantum master equation we obtain the energy- and time-resolved electron transfer through the device which resembles the measured data. The observed oscillations are found to depend on the level offset of the two dots during the manipulation and, most surprisingly, also the on initialization stage. By means of an analytical expression, obtained from a large-bias model, we can understand the prominent features of these oscillations seen in both the experimental data and the numerical results. These findings strengthen the common interpretation in terms of a coherent transfer of electrons between the dots. PACS numbers: 73.63.Kv,73.23.Hk,72.10.-d