State-dependent linear-optical qubit amplifier

Abstract

We propose a linear-optical setup for heralded qubit amplification with tunable output qubit fidelity. We study its success probability as a function of output qubit fidelity showing that at the expense of lower fidelity, the setup can considerably increase probability of successful operation. These results are subsequently applied in a proposal for state dependent qubit amplification. Similarly to state-dependent quantum cloning, the a priori information about the input state allows to optimize the qubit amplification procedure to obtain better fidelity versus success probability trade-off.Comment: 8 pages, 7 figure

Entanglement-Based Single-Photon Amplification With High Fidelity of Polarization Feature

“…It was shown that the success probability didn't decrease asymptotically to zero even with the increasing gain. Bartkiewicz et al studied the statedependent qubit amplification with success probability as a function of output qubit fidelity [26]. The qubit amplification procedure could be optimized to obtain better fidelity versus success probability.…”

Efficient amplification of photonic qubits by optimal quantum cloning

“…In the case of the originall proposal, perfect gain could have been reached only asymptotically, however this shortcomming has been removed by Pitkanen et al [7]. Recently, it has been shown that, if a heralded amplifier is allowed to introduce some noise, its gain and herading rate be increased [10] which also depends on the set of qubits to be amplified.…”

“…The heralded amplifier and its improvments (see, eg., Ref. [7]) or alternarive schemes using entanglement [8][9][10] have been demonstrated to be useful especially in the * bark@amu.edu.pl context of quantum key distribution. Interesingly the improved qubit amplifier described in Ref.…”

Optical amplification of single-photon polarization qubit using weak measurement

“…Single-photon amplification is a promising method to overcome the photon loss problem by amplifying the probability of non-vacuum state, 13) which can be achieved by using single-photon or entangled photon pairs as auxiliary. [14][15][16][17][18][19][20][21][22][23] Xiang et al experimentally demonstrated a nondeterministic single-photon-assisted noiseless linear amplifier and used it to entanglement distillation. 14) This scheme was heralded, and could create a freely-propagating amplified state forming the basis of practical quantum communication.…”

“…19) They achieved infinite gain with the success probability equal to that of standard teleportation, and presented its applications in entanglement distillation and quantum key distribution. Bartkiewicz et al presented a statedependent qubit amplification based on entanglement, 20) and its probability could be seen as a function of output fidelity. It was a trade-off between better fidelity and success probability to optimize the qubit amplification.…”