Zeno and Anti-Zeno Polarization Control of Spin Ensembles by Induced Dephasing | Phys. Rev. Lett. 105, 160401 (2010)

Zeno and Anti-Zeno Polarization Control of Spin Ensembles by Induced Dephasing

Gonzalo A. Álvarez1,2, D. D. Bhaktavatsala Rao3, Lucio Frydman3,*, and Gershon Kurizki3,†

1Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina

2Fakultät Physik, Universität Dortmund, Otto-Hahn-Strasse 4, D-44221 Dortmund, Germany

3Department of Chemical Physics, Weizmann Institute of Science, Rehovot, 76100, Israel

Received 26 May 2010; revised 19 July 2010; published 12 October 2010

We experimentally and theoretically demonstrate the purity (polarization) control of qubits entangled with multiple spins, using induced dephasing in nuclear magnetic resonance setups to simulate repeated quantum measurements. We show that one may steer the qubit ensemble towards a quasiequilibrium state of a certain purity by choosing suitable time intervals between dephasing operations. These results demonstrate that repeated dephasing at intervals associated with the anti-Zeno regime leads to ensemble purification, whereas those associated with the Zeno regime lead to ensemble mixing.

© 2010 The American Physical Society

via Phys. Rev. Lett. 105, 160401 (2010): Zeno and Anti-Zeno Polarization Control of Spin Ensembles by Induced Dephasing.

Time evolution of the system (S) spin polarization. The main panel compares S-spin polarization interrupted by repeated measurements at intervals of 1 ms (blue upper triangles) and the evolution interrupted at 0.2 ms (red circles), respectively. A quasiequilibrium state is achieved for the 1ms measurements, stopped after 8 ms and followed by free evolution at later times (green lower triangles). The S spin free evolution is shown with black squares. The inset zooms the dynamics for short times. The theoretical curves (dashed lines) are obtained by exact diagonalization of the Hamiltonian for the experimental parameters above.

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