Deterministic and cascadable conditional phase gate for photonic qubits
Abstract
Previous analyses of conditional φnl-phase gates for photonic qubits that treat cross-phase modulation (XPM) in a causal, multimode, quantum field setting suggest that a large (∼π rad) nonlinear phase shift is always accompanied by fidelity-degrading noise [J. H. Shapiro, Phys. Rev. A1050-294710.1103/PhysRevA.73.062305 73, 062305 (2006); J. Gea-Banacloche, Phys. Rev. A1050-294710.1103/PhysRevA.81.043823 81, 043823 (2010)]. Using an atomic ∨ system to model an XPM medium, we present a conditional phase gate that, for sufficiently small nonzero φnl, 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.
- Publication:
-
Physical Review A
- Pub Date:
- April 2013
- DOI:
- 10.1103/PhysRevA.87.042325
- arXiv:
- arXiv:1202.6640
- Bibcode:
- 2013PhRvA..87d2325C
- Keywords:
-
- 03.67.Lx;
- 42.50.Ex;
- 33.57.+c;
- 42.65.Hw;
- Quantum computation;
- Optical implementations of quantum information processing and transfer;
- Magnetooptical and electrooptical spectra and effects;
- Phase conjugation;
- photorefractive and Kerr effects;
- Quantum Physics
- E-Print:
- doi:10.1103/PhysRevA.87.042325