Decoherence time maximization and partial isolation for open quantum harmonic oscillator memory networks
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arXiv
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| Natura: | Preprint |
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2025
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| author | Vladimirov, Igor G. Petersen, Ian R. Shi, Guodong |
| author_facet | Vladimirov, Igor G. Petersen, Ian R. Shi, Guodong |
| contents | This paper considers a network of open quantum harmonic oscillators which interact with their neighbours through direct energy and field-mediated couplings and also with external quantum fields. The position-momentum dynamic variables of the network are governed by linear quantum stochastic differential equations associated with the nodes of a graph whose edges specify the interconnection of the component oscillators. Such systems can be employed as Heisenberg picture quantum memories with an engineered ability to approximately retain initial conditions over a bounded time interval. We use the quantum memory decoherence time defined previously in terms of a fidelity threshold on a weighted mean-square deviation for a subset (or linear combinations) of network variables from their initial values. This approach is applied to maximizing a high-fidelity asymptotic approximation of the decoherence time over the direct energy coupling parameters of the network. The resulting optimality condition is a set of linear equations for blocks of a sparse matrix associated with the edges of the direct energy coupling graph of the network. We also discuss a setting where the quantum network has a subset of dynamic variables which are affected by the external fields only indirectly, through a complementary ``shielding'' system. This holds under a rank condition on the network-field coupling matrix and can be achieved through an appropriate field-mediated coupling between the component oscillators. The partially isolated subnetwork has a longer decoherence time in the high-fidelity limit, thus providing a particularly relevant candidate for a quantum memory. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_20675 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Decoherence time maximization and partial isolation for open quantum harmonic oscillator memory networks Vladimirov, Igor G. Petersen, Ian R. Shi, Guodong Quantum Physics Systems and Control Optimization and Control 81S22, 81S25, 81P16, 81S05, 81Q93, 81R15, 81Q10, 81Q15, 81P40, 60G15, 05C90 This paper considers a network of open quantum harmonic oscillators which interact with their neighbours through direct energy and field-mediated couplings and also with external quantum fields. The position-momentum dynamic variables of the network are governed by linear quantum stochastic differential equations associated with the nodes of a graph whose edges specify the interconnection of the component oscillators. Such systems can be employed as Heisenberg picture quantum memories with an engineered ability to approximately retain initial conditions over a bounded time interval. We use the quantum memory decoherence time defined previously in terms of a fidelity threshold on a weighted mean-square deviation for a subset (or linear combinations) of network variables from their initial values. This approach is applied to maximizing a high-fidelity asymptotic approximation of the decoherence time over the direct energy coupling parameters of the network. The resulting optimality condition is a set of linear equations for blocks of a sparse matrix associated with the edges of the direct energy coupling graph of the network. We also discuss a setting where the quantum network has a subset of dynamic variables which are affected by the external fields only indirectly, through a complementary ``shielding'' system. This holds under a rank condition on the network-field coupling matrix and can be achieved through an appropriate field-mediated coupling between the component oscillators. The partially isolated subnetwork has a longer decoherence time in the high-fidelity limit, thus providing a particularly relevant candidate for a quantum memory. |
| title | Decoherence time maximization and partial isolation for open quantum harmonic oscillator memory networks |
| topic | Quantum Physics Systems and Control Optimization and Control 81S22, 81S25, 81P16, 81S05, 81Q93, 81R15, 81Q10, 81Q15, 81P40, 60G15, 05C90 |
| url | https://arxiv.org/abs/2503.20675 |