Optical coupling of two distant InAs/GaAs quantum dots by a photonic-crystal microcavity

Abstract

Long distance ͑1.4 m͒ interaction of two different InAs/GaAs quantum dots in a photonic crystal microcavity is observed. Simultaneous coupling of both quantum dots to the cavity is demonstrated by Purcell effect measurements. Resonant optical excitation in the p state of any of the quantum dots, results in an increase in the s-state emission of the other one. The cavity-mediated coupling can be controlled by varying the excitation intensity. These results represent an experimental step toward the realization of quantum logic operations using distant solid-state qubits. DOI: 10.1103/PhysRevB.81.193301 PACS number͑s͒: 78.67.Hc, 42.50.Ex, 78.67.De Efficient quantum information applications require qubits with low decoherence rates, fast manipulation times, and easy scalability.1 These requirements are met by qubits based on electron spins or excitons in semiconductor quantum dots ͑QDs͒. Coupling of single semiconductor QD excitons to a microcavity confined electromagnetic mode has different advantages depending on the coupling strength. Weak coupling allows enhanced optical efficiency associated to the exciton decay time reduction by the Purcell effect.2 In the strong-coupling regime, the system presents entangled lightmatter states that can be used as building blocks for transmission of quantum information, 3 qubit readout, 4 production of entangled pairs by compensation of the natural exciton fine structure splitting, 5 and lasing. 6 Single QD-cavity coupling has been demonstrated in the past years, 7-13 showing interesting cavity-quantum electrodynamics effects. The possibility of using two or more qubits coupled by a single optical microcavity is appealing for it can provide techniques for long distance, fast interactions between qubits.14-16 New dynamical phenomena are expected in these systems, which are dependent on the relative energy scales of the coupling between qubits and between qubits and the cavity mode ͑CM͒. In randomly distributed QDs samples it is statistically difficult to have two or more QDs both spatially and spectrally coupled to a microcavity mode. Some approaches have been proposed to obtain this type of coupled system, [17][18][19] which rely on the deterministic location of the QD in the cavity.12,20 Coupling of several QDs to a single cavity mode has been reported as the origin of lasing at very low threshold. 21In this Brief Report, we show that exciton states of two semiconductor quantum dots with large lateral separation interact through a microcavity confined optical mode. Individual and simultaneous coupling of the QDs to the CM is demonstrated by changes in photoluminescence ͑PL͒ emission intensity and spontaneous emission rate ͑Purcell effect͒ when the QD excitons are brought into resonance with the CM. Cavity-mediated inter-QD interaction is demonstrated by PL excitation ͑PLE͒ measurements, in which resonant excitation at the p state of any of the QDs increases the s-state emission of the other one. The microcavity-mediated interaction of the two QDs can be controlled by vary...

Two-photon spectra of quantum emitters

“…Two coupled single-mode emitters account for, or are at the heart of, a large gamut of quantum optical systems. We will consider three paradigmatic cases, the subjects of intense theoretical and experimental studies: two coupled harmonic oscillators [28,29], two coupled two-level systems [30][31][32][33] and the Jaynes-Cummings model [8,[34][35][36][37][38] where one harmonic oscillator is coupled to a two-level system. All of them are described by the following Hamiltonian: where, as in the previous section, O 1,2 describes two modes that can be either a harmonic oscillator or a two-level system.…”

Luminescence spectra of quantum dots in microcavities. III. Multiple quantum dots

“…[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] The possibility of coupling strongly more than one quantum dot to the (still single) microcavity mode [40][41][42][43][44][45][46][47][48] is starting to emerge experimentally, 4,19,49,50 as technology makes always more accessible the design and control of complex configurations with multiple quantum dots. 51,52 The rich physics of the single-quantum-dot case is thus finding an even richer and wider arena where N > 1 dots are simultaneously involved.…”

Quantum calculations on quantum dots in semiconductor microcavities. Part III

“…Unfortunately, the authors of the mentioned studies said nothing about the distance between QDs and limited the consideration to the spectroscopy observations. The interaction between two InAs/GaAs QDs through the photon exchange via the PC MC mode (Q ≈ 3000) was also experimentally demon strated in [18]. The successful implementation of the two qubit CNOT operation in the exciton photon basis was reported in a recent work [19].…”