Protecting subspaces by acting on the outside

Busch, Jonathan; Beige, Almut

doi:10.1088/1742-6596/254/1/012009

Cited by 8 publications

(13 citation statements)

References 46 publications

(68 reference statements)

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“…Our result clearly shows that the quantum Zeno effect and the dynamical decoupling can have rather different results when the operation frequency is finite, though the two methods give essentially the same results in the limit of infinite operation frequent as shown in Ref. [22][23][24].…”

Section: Concluding Remarksupporting

confidence: 73%

“…It is therefore an interesting problem to study how one could protect a two-qubit state with techniques which have been demonstrated already, for example, dynamical decoupling scheme [11][12][13][14][15][16]18] which have been demonstrated experimentally recently [19][20][21]. It is well known that in the limit of infinitely frequent operations, QZE and dynamical decoupling are unified and can have the same results [22][23][24]. The two methods are not compared in the more realistic condition when the operation frequencies are finite.…”

Section: Introductionmentioning

confidence: 99%

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Protecting two-qubit quantum states byπ-phase pulses

Wang

Kwek

2010

Phys. Rev. A

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We study the state decay of two qubits interacted with a common harmonic oscillator reservoir. There are both decoherence error and the error caused by the amplitude change of the superradiant state. We show that frequent π-phase pulses can eliminate both typpes of errors therefore protect a two-qubit odd-parity state more effectively than the frequent measurement method. This shows that the the methods using dynamical decoupling and the quantum Zeno effects actually can give rather different results when the operation frequency is finite.

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Section: Concluding Remarksupporting

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Protecting two-qubit quantum states byπ-phase pulses

Wang

Kwek

2010

Phys. Rev. A

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“…Subtle quantum effects are known to be able to populate certain states of the system selectively, while leaving others empty. [8][9][10][11][12] A canonical example is the Λ system, in which excitation can be transferred directly via a Stimulated Raman Adiabatic Passage (STIRAP) from an initial to a final ground state. 13,14 Even though these states are not directly coupled but only interact indirectly via a single excited state, this intermediate bridge does not acquire any population.…”

Section: Introductionmentioning

confidence: 99%

“…Rapid dynamics can be shown to effectively result in a quantum Zeno effect which suppresses the exchange of excitation between observed subspace. 10,11 For example, STIRAP works because the above described Λ system possesses a zero energy eigenstate. The presence of strong interactions ensures that the Λ system remains at all times in its zero eigenstate.…”

Section: Introductionmentioning

confidence: 99%

Efficient long-distance energy transport in molecular systems through adiabatic passage

Dijkstra

Beige

2019

The Journal of Chemical Physics

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The efficiencies of light-harvesting complexes in biological systems can be much higher than the current efficiencies of artificial solar cells. In this paper, we therefore propose and analyse an energy transport mechanism which employs adiabatic passages between the states of an artificially designed antenna molecular system to significantly enhance the conversion of incoming light into internal energy. It is shown that the proposed transport mechanism is relatively robust against spontaneous emission and de-phasing, while also being able to take advantage of collective effects. Our aim is to provide new insight into the energy transport in molecular complexes and to improve the design of solar cells.

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“…If the measurements project the system back into a finitedimensional subspace that includes the initial state, the state evolution remains confined within this subspace and the subspace can be protected against leakage of population using a quantum Zeno strategy [4,5]. An operator version of this phenomenon has also been suggested recently [6,7].…”

Section: Introductionmentioning

confidence: 99%

Experimental protection against evolution of states in a subspace via a super-Zeno scheme on an NMR quantum information processor

2014

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We experimentally demonstrate the freezing of evolution of quantum states in one-and two-dimensional subspaces of two qubits, on an NMR quantum information processor. State evolution was frozen and leakage of the state from its subspace to an orthogonal subspace was successfully prevented using super-Zeno sequences [Phys. Rev. Lett. 96, 100405 (2006)], comprising a set of radio frequency (rf) pulses punctuated by pre-selected time intervals. We demonstrate the efficacy of the scheme by preserving different types of states, including separable and maximally entangled states in one-and two-dimensional subspaces of two qubits. The change in the experimental density matrices was tracked by carrying out full state tomography at several time points. We use the fidelity measure for the one-dimensional case and the leakage (fraction) into the orthogonal subspace for the two-dimensional case, as qualitative indicators to estimate the resemblance of the density matrix at a later time to the initially prepared density matrix. For the case of entangled states, we additionally compute an entanglement parameter to indicate the presence of entanglement in the state at different times. We experimentally demonstrate that the super-Zeno scheme is able to successfully confine state evolution to the one-or two-dimensional subspace being protected.

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Protecting subspaces by acting on the outside

Cited by 8 publications

References 46 publications

Protecting two-qubit quantum states byπ-phase pulses

Protecting two-qubit quantum states byπ-phase pulses

Efficient long-distance energy transport in molecular systems through adiabatic passage

Experimental protection against evolution of states in a subspace via a super-Zeno scheme on an NMR quantum information processor

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