12 September 2014 Controlling a photon with a solid-state quantum bit
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Generating strong interactions between single quanta of light and matter is central to quantum information science, and a key component of quantum computers and long-distance quantum networks. In quantum information processing, these interactions are required to create elementary logic operations (quantum gates) between stationary matter quantum bits (qubits) and photonic qubits that can be transmitted over long distances. Efficient quantum gates between photonic and matter qubits are a crucial enabler for a broad range of applications that include robust quantum networks, nondestructive quantum measurements, and strong photon-photon interactions. So far these qubit-photon gates have been achieved using single atoms and at microwave frequencies in circuit QED systems. Their implementation with solidstate quantum emitters, however, has remained a difficult challenge. We demonstrate that the qubit state of a photon can be controlled by a single solid-state qubit composed of a quantum dot (QD) strongly coupled to an optical nanocavity. We show that the QD acts as a coherently controllable qubit system that conditionally flips the polarization of a photon reflected from the cavity mode on picosecond timescales. This operation implements a controlled NOT (cNOT) logic gate between the QD and the incident photon, which is a universal quantum operation that can serve as a general light-matter interface for remote entanglements and quantum computations. Our results represent an important step towards an all solid-state implementation of quantum networks and quantum computers, and provide a versatile approach for controlling and probing interactions between a photon and a single quantum emitter on ultra-fast timescales.
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Edo Waks, Edo Waks, Hyochul Kim, Hyochul Kim, Ranojoy Bose, Ranojoy Bose, Tao Cai, Tao Cai, Shuo Sun, Shuo Sun, Glenn S. Solomon, Glenn S. Solomon, "Controlling a photon with a solid-state quantum bit", Proc. SPIE 9162, Active Photonic Materials VI, 91620A (12 September 2014); doi: 10.1117/12.2061333; https://doi.org/10.1117/12.2061333

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