Efficient amplification of photonic qubits by optimal quantum cloning

Bartkiewicz, Karol; Cernoch, A; Lemr, Karel; Soubusta, Jan; Stobińska, Magdalena

doi:10.1103/physreva.89.062322

Cited by 16 publications

(17 citation statements)

References 43 publications

(70 reference statements)

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“…In this Figure, we plot the exact path taken by the Nelder-Mead simplex algorithm to minimize the cost function C for the case of a real experiment and its simulation. The selected initial simplex was intentionally chosen well away from the optimal position -its first vertex resembles the trivial cloning strategy [24,28]. In Figure 3a, we illustrate the evolution of both the fidelities F 1 and F 2 during the training.…”

Section: Resultsmentioning

confidence: 99%

Experimental hybrid quantum-classical reinforcement learning by boson sampling: how to train a quantum cloner

et al. 2019

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We report on experimental implementation of a machine-learned quantum gate driven by a classical control. The gate learns optimal phase-covariant cloning in a reinforcement learning scenario having fidelity of the clones as reward. In our experiment, the gate learns to achieve nearly optimal cloning fidelity allowed for this particular class of states. This makes it a proof of present-day feasibility and practical applicability of the hybrid machine learning approach combining quantum information processing with classical control. Moreover, our experiment can be directly generalized to larger interferometers where the computational cost of classical computer is much lower than the cost of boson sampling.

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Section: Resultsmentioning

confidence: 99%

Experimental hybrid quantum-classical reinforcement learning by boson sampling: how to train a quantum cloner

et al. 2019

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“…Post-selection is a well established technique in quantum state engineering used, e.g., in optimal quantum cloning [12]. Here, the post-selection on the photon that interacted with mirror A is formally equivalent to the projection of the output state onto the state…”

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confidence: 99%

One-state vector formalism for the evolution of a quantum state through nested Mach-Zehnder interferometers

et al. 2015

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Linear-optical interferometers play a key role in designing circuits for quantum information processing and quantum communications. Even though nested Mach-Zehnder interferometers appear easy to describe, there are occasions when they provide unintuitive results. This paper explains the results of a highly discussed experiment performed by Danan et al. [Phys. Rev. Lett. 111, 240402 (2013)] using a standard approach. We provide a simple and intuitive one-state vector formalism capable of interpreting their experiment. Additionally, we cross-checked our model with a classical-physics based approach and found that both models are in complete agreement. We argue that the quantity used in the mentioned experiment is not a suitable which-path witness producing seemingly contra-intuitive results. To circumvent this issue, we establish a more reliable which-path witness and show that it yields well expected outcomes of the experiment. In quantum mechanics (QM) particles are assigned a wave function used to describe their properties [1]. This approach sometimes leads to conclusions about experimental results that seem to contradict intuitive estimations based on classical physics [2,3]. Despite this flaw, QM is currently widely accepted as a theory [1,4], that makes accurate predictions in agreement with the performed experiments. Therefore, it is considered valid regularly used for the interpretation of the results of the corresponding experiments.Recently, an experiment that contained counterintuitive features was proposed and realized by Danan et al. [5]. The authors used nested Mach-Zehnder interferometers (MZI), shown in Fig. 1, and mirrors (A, B, C, E, F) vibrating with different frequencies, in order to leave a mark on passing photons. At one selected output port of the interferometer, the photons were detected by a quad-cell detector D capable of tracing the spatial vibrations of the photon beam. After measurement, the collected signal was further processed and subjected to the Fourier transform. From the obtained frequencies of vibrations, the authors judged whether the detected photons have interacted with the mirror that was oscillating at this particular frequency.The results described in the article by Danan et al. ence inside the interferometer, the correct application of TSVF, the processing of the obtained data and its validity. Until now, no-one has managed to provide the theoretical calculations and the interpretation of the experimental results using only the standard one-state vec-

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“…In contrast to amplification, cloning schemes are usually optimized to maximize fidelity given certain a priori information, disregarding other parameters such as the success probability of the cloning operation. In case of quantum cloning, the analysis of the fidelity vs success probability trade-off has been investigated, for instance, in a recent paper on cloning-based amplification [37]. In the relevant paper, fidelity and probability of success are optimized by switching between optimal probabilistic quantum cloning and deterministic classical cloning based on the measure and reproduce method.…”

Section: Discussionmentioning

confidence: 99%

State-dependent linear-optical qubit amplifier

2013

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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

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Efficient amplification of photonic qubits by optimal quantum cloning

Cited by 16 publications

References 43 publications

Experimental hybrid quantum-classical reinforcement learning by boson sampling: how to train a quantum cloner

Experimental hybrid quantum-classical reinforcement learning by boson sampling: how to train a quantum cloner

One-state vector formalism for the evolution of a quantum state through nested Mach-Zehnder interferometers

State-dependent linear-optical qubit amplifier

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