Generation of entangled ancilla states for use in linear optics quantum computing

Abstract

Quantum logic operations can be performed using linear optical elements, additional photons (ancilla photons), and postselection based on measurements made on the ancilla. Here we describe a method for generating the required entangled state of n ancilla photons using elementary logic gates and postselection. This approach is capable of generating the ancilla states required for either the original proposal by Knill, Laflamme, and Milburn [E. Knill, R. Laflamme, and G. J. Milburn, Nature 409, 46 (2001)] or those required for the more general high-fidelity approach [J. D. Franson, M. M. Donegan, M. J. Fitch, B. C. Jacobs, and T. B. Pittman, Phys. Rev. Lett. 89, 137901 (2002)]. We also show that the entangled ancilla photons could be generated using a series of quantum wells coupled with tunnel junctions.

Simple circuit of linear optics logic gates

“…Despite these limitations the circuit shown in Figure 1 can be useful, for example, in determining the parity of three qubits, or assisting in the generation of certain nonclassical states of light. 8 The remainder of the paper is organized as follows. In section 2, we review how the individual XOR gates work, highlighting their reliance on two-photon interference effects.…”

Generation of two-atom Knill–Laflamme–Milburn states with cavity quantum electrodynamics

“…Employing the KLM states as ancillary resources, one can improve the success probability of teleportation gradually closed to unity with the increase of the particle number in these ancillary states and then enhance the efficiency of the KLM-type quantum computation. Afterwards, manifold proposals have been presented to generate the original or transformative KLM states and elaborate the related quantum computation [13][14][15][16][17][18]. Franson et al proposed two theoretical schemes to generate the arbitrary photonnumber KLM states using elementary linear-optics gates and solid-state approach, respectively [13].…”

“…Afterwards, manifold proposals have been presented to generate the original or transformative KLM states and elaborate the related quantum computation [13][14][15][16][17][18]. Franson et al proposed two theoretical schemes to generate the arbitrary photonnumber KLM states using elementary linear-optics gates and solid-state approach, respectively [13]. Two-photon KLM states were also considered in a class of adaptive teleportation scheme to increase the probability of faithful teleportation [17], and the authors stated nonmaximally entangled KLM states were more applicable than maximally entangled ones in the sense of success probability for some specific situations.…”

Engineering steady Knill-Laflamme-Milburn state of Rydberg atoms by dissipation

“…Recently, researchers pay close attention to preparing and extending photonic KLM states [10][11][12][13]. Concretely, Franson et al made use of elementary linear-optics gates and solid-state approach to produce the arbitrary photon-number KLM states [10]. In addition, Lemr et al proposed two ways for preparation of the KLM state using spontaneous parametric down-conversion in experiment and employing a tunable controlled phase gate in theory, respectively [12,13].…”