Deterministic and cascadable conditional phase gate for photonic qubits
Author(s)Chudzicki, Christopher Alan; Shapiro, Jeffrey H.; Chuang, Isaac L.
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Previous analyses of conditional φ[subscript nl]-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. A 73, 062305 (2006); J. Gea-Banacloche, Phys. Rev. A 81, 043823 (2010)]. Using an atomic ∨ system to model an XPM medium, we present a conditional phase gate that, for sufficiently small nonzero φ[subscript 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.
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science; Massachusetts Institute of Technology. Department of Physics; Massachusetts Institute of Technology. Research Laboratory of Electronics
Physical Review A
American Physical Society
Chudzicki, Christopher, Isaac L. Chuang, and Jeffrey H. Shapiro. "Deterministic and cascadable conditional phase gate for photonic qubits." Phys. Rev. A 87, 042325 (April 2013). © 2013 American Physical Society
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