dorsal/arxiv
View SchemaPrinciples of Control for Decoherence-Free Subsystems
| Authors | P. Cappellaro, J. S. Hodges, T. F. Havel, D. G. Cory |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0604203 |
| URL | https://arxiv.org/abs/quant-ph/0604203 |
| DOI | 10.1063/1.2216702 |
| Journal | J. Chem. Phys. 125, 044514 (2006) |
Abstract
Decoherence-Free Subsystems (DFS) are a powerful means of protecting quantum information against noise with known symmetry properties. Although Hamiltonians theoretically exist that can implement a universal set of logic gates on DFS encoded qubits without ever leaving the protected subsystem, the natural Hamiltonians that are available in specific implementations do not necessarily have this property. Here we describe some of the principles that can be used in such cases to operate on encoded qubits without losing the protection offered by the DFS. In particular, we show how dynamical decoupling can be used to control decoherence during the unavoidable excursions outside of the DFS. By means of cumulant expansions, we show how the fidelity of quantum gates implemented by this method on a simple two-physical-qubit DFS depends on the correlation time of the noise responsible for decoherence. We further show by means of numerical simulations how our previously introduced "strongly modulating pulses" for NMR quantum information processing can permit high-fidelity operations on multiple DFS encoded qubits in practice, provided that the rate at which the system can be modulated is fast compared to the correlation time of the noise. The principles thereby illustrated are expected to be broadly applicable to many implementations of quantum information processors based on DFS encoded qubits.
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"abstract": "Decoherence-Free Subsystems (DFS) are a powerful means of protecting quantum\ninformation against noise with known symmetry properties. Although Hamiltonians\ntheoretically exist that can implement a universal set of logic gates on DFS\nencoded qubits without ever leaving the protected subsystem, the natural\nHamiltonians that are available in specific implementations do not necessarily\nhave this property. Here we describe some of the principles that can be used in\nsuch cases to operate on encoded qubits without losing the protection offered\nby the DFS. In particular, we show how dynamical decoupling can be used to\ncontrol decoherence during the unavoidable excursions outside of the DFS. By\nmeans of cumulant expansions, we show how the fidelity of quantum gates\nimplemented by this method on a simple two-physical-qubit DFS depends on the\ncorrelation time of the noise responsible for decoherence. We further show by\nmeans of numerical simulations how our previously introduced \"strongly\nmodulating pulses\" for NMR quantum information processing can permit\nhigh-fidelity operations on multiple DFS encoded qubits in practice, provided\nthat the rate at which the system can be modulated is fast compared to the\ncorrelation time of the noise. The principles thereby illustrated are expected\nto be broadly applicable to many implementations of quantum information\nprocessors based on DFS encoded qubits.",
"arxiv_id": "quant-ph/0604203",
"authors": [
"P. Cappellaro",
"J. S. Hodges",
"T. F. Havel",
"D. G. Cory"
],
"categories": [
"quant-ph"
],
"doi": "10.1063/1.2216702",
"journal_ref": "J. Chem. Phys. 125, 044514 (2006)",
"title": "Principles of Control for Decoherence-Free Subsystems",
"url": "https://arxiv.org/abs/quant-ph/0604203"
},
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