Deterministic and cascadable conditional phase gate for photonic qubits

作者：Chudzicki Christopher^*; Chuang Isaac L; Shapiro Jeffrey H

来源：Physical Review A, 2013, 87(4): 042325.

DOI：10.1103/PhysRevA.87.042325

Previous analyses of conditional phi(NL)-phase gates for photonic qubits that treat cross-phase modulation (XPM) in a causal, multimode, quantum field setting suggest that a large (similar to pi rad) nonlinear phase shift is always accompanied by fidelity-degrading noise [J. H. Shapiro, Phys. Rev. A 73, 062305 (2006); J. Gea-Banacloche, ibid. 81, 043823 (2010)]. Using an atomic. system to model an XPM medium, we present a conditional phase gate that, for sufficiently small nonzero phi(NL), has high fidelity. The gate is made cascadable by using a special measurement, i.e., principal-mode projection, to exploit the quantum Zeno effect and preclude the accumulation of fidelity-degrading departures from the principal-mode Hilbert space when both control and target photons illuminate the gate. The nonlinearity of the. system we study is too weak for this particular implementation to be practical. Nevertheless, the idea of cascading through principal-mode projection is of potential use to overcome fidelity-degrading noise for a wide variety of nonlinear optical primitive gates. DOI: 10.1103/PhysRevA.87.042325

• 出版日期2013-4-22