Optimal copying of one quantum bit

Analysis of one quantum bit string commitment

A. Kent proposed a quantum bit string commitment protocol in 2003. Not using the standard two conjugate states |0〉, |1〉, |+〉 and |−〉, the protocol uses ψ0 = |0〉 and ψ1 = sin θ|0〉 + cos θ|1〉, where θ 6= 0. In this paper, we show that the protocol can not guarantee security to the receiver. (1 − sin2 θ 2 )n bits are definitely exposed to the receiver, where n is the length of the committed string.

Power of One Bit of Quantum Information in Quantum Metrology

Bit Copying - The Ultimate Computational Simplicity

This paper presents a proof that referencing and bit copying operations are sufficient for Turing-complete computation. A programming language consisting of just one instruction – bit copy, is presented. This language is powerful enough to run programs such as “Hello, World!” with iterations over an array and calculating factorials. The idea is that the computation is done without logic operati...

Hamiltonian for Quantum Copying

We derive an explicit Hamiltonian for copying the basis up and down states of a quantum two-state system—a qubit—onto n " copy " qubits (n ≥ 1) initially all prepared in the down state. In terms of spin components , for spin-1 2 particle spin states, the resulting Hamiltonian involves n-and (n + 1)-spin interactions. The case n = 1 also corresponds to a quantum-computing controlled-NOT gate.

Quantum copying: A network

V. Bužek, S. L. Braunstein, M. Hillery, and D. Bruß 1 Optics Section, The Blackett Laboratory, Imperial College, London SW7 2BZ, United Kingdom 2 Institute of Physics, Slovak Academy of Sciences, Dubravská cesta 9, 842 28 Bratislava, Slovakia 3 University of Wales, Dean Street, Bangor LL57 1UT, United Kingdom 4 Department of Physics and Astronomy, Hunter College, CUNY, 695 Park Avenue, New York...