Demonstration of a Quantum Controlled-NOT Gate in the Telecommunications Band
Jun Chen, Joseph B. Altepeter, Milja Medić, Kim Fook Lee, Burç Gökden, Robert H. Hadfield, Sae Woo Nam, Prem Kumar · Physical Review Letters · 2008
We present the first quantum controlled-not (cnot) gate realized using a fiber-based indistinguishable photon-pair source in the 1.55 microm telecommunications band. Using this free-space cnot gate, all four Bell states are produced and fully characterized by performing quantum-state tomography, demonstrating the gate's unambiguous entangling capability and high fidelity. Telecom-band operation makes this cnot gate particularly suitable for quantum-information-processing tasks that are at the interface of quantum communication and linear optical quantum computing.