Demonstration of a Fundamental Quantum Logic Gate
Christopher R. Monroe, D. M. Meekhof, B. E. King, Wayne M. Itano, David J. Wineland · Physical Review Letters · 1995
We demonstrate the operation of a two-bit "controlled-NOT" quantum logic gate, which, in conjunction with simple single-bit operations, forms a universal quantum logic gate for quantum computation. The two quantum bits are stored in the internal and external degrees of freedom of a single trapped atom, which is first laser cooled to the zero-point energy. Decoherence effects are identified for the operation, and the possibility of extending the system to more qubits appears promising.