排序方式: 共有45条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
Y. Sharf D. G. Cory S. S. Somaroo T. F. Havel E. Knill R. Laflamme 《Molecular physics》2013,111(17):1347-1363
Quantum error correcting codes enable the information contained in a quantum state to be protected from decoherence due to external perturbations. Applied to NMR, this procedure does not alter normal relaxation, but rather converts the state of a 'data' spin into multiple quantum coherences involving additional ancilla spins. These multiple quantum coherences relax at differing rates, thus permitting the original state of the data to be approximately reconstructed by mixing them together in an appropriate fashion. This paper describes the operation of a simple, three-bit quantum code in the product operator formalism, and uses geometric algebra methods to obtain the error-corrected decay curve in the presence of arbitrary correlations in the external random fields. These predictions are confirmed in both the totally correlated and uncorrelated cases by liquid-state NMR experiments on 13C-labelled alanine, using gradient-diffusion methods to implement these idealized decoherence models. Quantum error correction in weakly polarized systems requires that the ancilla spins be prepared in a pseudo-pure state relative to the data spin, which entails a loss of signal that exceeds any potential gain through error correction. Nevertheless, this study shows that quantum coding can be used to validate theoretical decoherence mechanisms, and to provide detailed information on correlations in the underlying NMR relaxation dynamics. 相似文献
35.
We study finite dimensional partition properties of the countable homogeneous dense local order (a directed graph closely
related to the order structure of the rationals). Some of our results use ideas borrowed from the partition calculus of the
rationals and are obtained thanks to a strengthening of Milliken’s theorem on trees. 相似文献
36.
Chen TY Zhang J Boileau JC Jin XM Yang B Zhang Q Yang T Laflamme R Pan JW 《Physical review letters》2006,96(15):150504
We present an experimental realization of a robust quantum communication scheme [Phys. Rev. Lett. 93, 220501 (2004)] using pairs of photons entangled in polarization and time. Our method overcomes errors due to collective rotation of the polarization modes (e.g., birefringence in optical fiber or misalignment), is insensitive to the phase's fluctuation of the interferometer, and does not require any shared reference frame including time reference, except the need to label different photons. The practical robustness of the scheme is further shown by implementing a variation of the Bennett-Brassard 1984 quantum key distribution protocol over 1 km optical fiber. 相似文献
37.
38.
39.
40.