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arXiv:1911.11585 · Optica

Photonic realization of quantum resetting

Zheng-Da Li, Xu-Fei Yin, Zizhu Wang, Li-Zheng Liu, Rui Zhang, Yu-Zhe Zhang, Xiao Jiang, Jun Zhang, Li Li, Nai-Le Liu, Xiao-Bo Zhu, Feihu Xu, Yu-Ao Chen, Jian-Wei Pan

Published Jun 11, 2020• 7 citations
arXivHTMLPDF

Abstract

Contrary to the usual assumption of at least partial control of quantum dynamics, a surprising recent result proved that an arbitrary quantum state can be probabilistically reset to a state in the past by having it interact with probing systems in a consistent butuncontrolledway. We present a photonic implementation to achieve this resetting process, experimentally verifying that a state can be probabilistically reset to its past with a fidelity of 0.870±0.012 . We further demonstrate the preservation of an entangled state, which still violates a Bell inequality, after half of the entangled pair was reset. The ability to reset uncontrolled quantum states has implications in the foundations of quantum physics and applications in areas of quantum technology.

DOI
10.1364/optica.389322

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•Jun 22, 2026•0 citations
Contrary to the usual assumption of at least partial control of quantum dynamics, a surprising recent result proved that an arbitrary quantum state can be probabilistically reset to a state in the past by having it interact with probing systems in a consistent butuncontrolledway. We present a photonic implementation to achieve this resetting process, experimentally verifying that a state can be probabilistically reset to its past with a fidelity of 0.870±0.012 . We further demonstrate the preservation of an entangled state, which still violates a Bell inequality, after half of the entangled pair was reset. The ability to reset uncontrolled quantum states has implications in the foundations of quantum physics and applications in areas of quantum technology.
In quantum mechanics, the unitary nature of time evolution makes it intrinsically reversible, given control over the system in question. Remarkably, there have been several recent demonstrations of protocols for reverting unknown unitaries in scenarios where even the interactions with the target system are unknown. These protocols are limited by their probabilistic nature, raising the fundamental question of whether time-reversal could be performed deterministically. Here we show that quantum physics indeed allows for this by exploiting the non-commuting nature of quantum operators, and demonstrate a recursive protocol for two-level quantum systems with an arbitrarily high probability of success. Using a photonic platform, we achieve an average rewinding fidelity of over 95%. Our protocol, requiring no knowledge of the quantum process to be rewound, is optimal in its running time, and brings quantum rewinding into a regime of practical relevance.
Abstract Quantum resetting protocols allow a quantum system to be sent to a state in the past by making it interact with quantum probes when neither the free evolution of the system nor the interaction is controlled. We experimentally verify the simplest non-trivial case of a quantum resetting protocol, known as the W4{{\mathcal{W}}}_{4}W4​ W 4 protocol, with five superconducting qubits, testing it with different types of free evolutions and target–probe interactions. After projection, we obtained a reset state fidelity as high as 0.951, and the process fidelity was found to be 0.792. We also implemented 100 randomly chosen interactions and demonstrated an average success probability of 0.323 for ∣1⟩\left|1\right\rangle∣1⟩ 1 and 0.292 for ∣−⟩\left|-\right\rangle∣−⟩ − , and experimentally confirmed the nonzero probability of success for unknown interactions; the numerical simulated values are about 0.3. Our experiment shows that the simplest quantum resetting protocol can be implemented with current technologies, making such protocols a valuable tool in the eternal fight against unwanted evolution in quantum systems.
We investigate the preservation and dynamics of entanglement and Bell nonlocality in a two-photon system subject to local dephasing, particularly emphasizing environments exhibiting non-Markovian memory effects. By analyzing the interplay between entanglement, as measured by concurrence, and Bell inequality violation, we identify time regions where Bell inequality is not violated, even when concurrence remains high. This indicates that strongly entangled states do not always exhibit nonclassical correlations with certainty. Our study further explores the effects of refractive index variations, spectral width, and interaction symmetry, demonstrating how structured environments and controlled environmental interactions can mitigate decoherence and enhance the resilience of quantum correlations. We propose that these theoretical predictions can be tested using modifications of recent experimental optical setups. These findings provide valuable insights into the conditions under which quantum correlations remain irreproducible by classical local hidden-variable models, with direct implications for quantum communication, quantum information processing, and foundational studies in quantum mechanics. Furthermore, our findings highlight the crucial importance of quantum coherence in maintaining entanglement and nonlocality over extended time evolution. These results show remarkable alignment with the experimental observations, demonstrating high accuracy and consistency within the expected parameter range.
As one of the most intriguing intrinsic properties of the quantum world, quantum superposition provokes great interest in its own generation. Though a universal quantum machine that creates superposition of two arbitrary unknown states has been shown to be physically impossible, a probabilistic protocol exists given that two input states have nonzero overlaps with the referential state. Here we report a probabilistic quantum machine realizing superposition of two arbitrary unknown photonic qubits as long as they have nonzero overlaps with the horizontal polarization state $|H\ensuremath{\rangle}$. A total of 11 different qubit pairs are chosen to test this protocol and we obtain the average fidelity as high as 0.99, which shows the excellent reliability of our realization. This realization may have significant applications in quantum information and quantum computation, e.g., generating nonclassical states and realizing information compression in a quantum computation.
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