PHYSICAL REVIEW LETTERS
Entangling Quantum-Logic Gate Operated with an Ultrabright Semiconductor Single-Photon Source
O. Gazzano, M. P. Almeida, A. K. Nowak, S. L. Portalupi, A. Lemaître, I. Sagnes, A. G. White, and P. Senellart
We have entangled two independent single photons emitted by a quantum dot using a quantum-logic gate.
A quantum controlled NOT (C-NOT) gate is a crucial element for quantum information processing. It is a two-qubit gate that flips the state of a target qubit depending on the state of a control one. The quantum capability of the gate allows creating an entangled two-qubit output state from independent input qubits. We use an ultrabright solid-state single photon source made by inserting a single quantum dots in a pillar microcavity. The truth table of the gate is measured in rectilinear basis and shows a probability of obtaining the correct output of 68% for a source brightness of 0.55 collected photon per pulse. By setting the control photon in diagonal basis, we show that the two output photons can be entangled. The fidelity to the Bell state is above the 0.5 limit for quantum correlation for a source brightness of 50% and reaches 71% for short time delays.