Post-processed estimation of quantum state trajectories
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arXiv
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| Hauptverfasser: | , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866915578893041664 |
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| author | Khademi, Soroush Slim, Jesse J. Laverick, Kiarn T. Chang, Jin Guo, Jingkun Gröblacher, Simon Wiseman, Howard M. Bowen, Warwick P. |
| author_facet | Khademi, Soroush Slim, Jesse J. Laverick, Kiarn T. Chang, Jin Guo, Jingkun Gröblacher, Simon Wiseman, Howard M. Bowen, Warwick P. |
| contents | Weak quantum measurements enable real-time tracking and control of dynamical quantum systems, producing quantum trajectories -- evolutions of the quantum state of the system conditioned on measurement outcomes. For classical systems, the accuracy of trajectories can be improved by incorporating future information, a procedure known as smoothing. Here we apply this concept to quantum systems, generalising a formalism of quantum state smoothing for an observer monitoring a quantum system exposed to environmental decoherence, a scenario important for many quantum information protocols. This allows future data to be incorporated when reconstructing the trajectories of quantum states. We experimentally demonstrate that smoothing improves accuracy using a continuously measured nanomechanical resonator, showing that the method compensates for both gaps in the measurement record and inaccessible environments. We further observe a key predicted departure from classical smoothing: quantum noise renders the trajectories nondifferentiable. These results establish that future information can enhance quantum trajectory reconstruction, with potential applications across quantum sensing, control, and error correction. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2510_16754 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Post-processed estimation of quantum state trajectories Khademi, Soroush Slim, Jesse J. Laverick, Kiarn T. Chang, Jin Guo, Jingkun Gröblacher, Simon Wiseman, Howard M. Bowen, Warwick P. Quantum Physics Weak quantum measurements enable real-time tracking and control of dynamical quantum systems, producing quantum trajectories -- evolutions of the quantum state of the system conditioned on measurement outcomes. For classical systems, the accuracy of trajectories can be improved by incorporating future information, a procedure known as smoothing. Here we apply this concept to quantum systems, generalising a formalism of quantum state smoothing for an observer monitoring a quantum system exposed to environmental decoherence, a scenario important for many quantum information protocols. This allows future data to be incorporated when reconstructing the trajectories of quantum states. We experimentally demonstrate that smoothing improves accuracy using a continuously measured nanomechanical resonator, showing that the method compensates for both gaps in the measurement record and inaccessible environments. We further observe a key predicted departure from classical smoothing: quantum noise renders the trajectories nondifferentiable. These results establish that future information can enhance quantum trajectory reconstruction, with potential applications across quantum sensing, control, and error correction. |
| title | Post-processed estimation of quantum state trajectories |
| topic | Quantum Physics |
| url | https://arxiv.org/abs/2510.16754 |