Evolutionary optimization of state selective field ionization for quantum computing

Jones, Martin L.; Sanguinetti, Bruno; Majeed, H. O.; Varcoe, Benjamin T. H.

doi:10.1016/j.asoc.2010.07.005

“…A final projective measurement which determines the energy level of the atom would be required. This is commonly done by means of state selective field-ionization detection [30][31][32][33], which involves passing the Rydberg atoms through an increasing electric field and measuring the energy at which the atom is ionized.…”

Section: A Cavity Qed Implementationmentioning

confidence: 99%

“…The Bell measurement can be performed with a combination of the operations in Eqs. (31), (32), and (34). This will yield a transformation which rotates each of the Bell states into some permutation of the computational basis states up to global phases.…”

Section: B Cavity Qed Realizationmentioning

confidence: 99%

See 1 more Smart Citation

Quantum measurements of atoms using cavity QED

Dada

¹

,

Andersson

²

,

Jones

³

et al. 2011

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Generalized quantum measurements are an important extension of projective or von Neumann measurements, in that they can be used to describe any measurement that can be implemented on a quantum system. We describe how to realize two non-standard quantum measurements using cavity quantum electrodynamics (QED). The first measurement optimally and unabmiguously distinguishes between two non-orthogonal quantum states. The second example is a measurement that demonstrates superadditive quantum coding gain. The experimental tools used are single-atom unitary operations effected by Ramsey pulses and two-atom Tavis-Cummings interactions. We show how the superadditive quantum coding gain is affected by errors in the field-ionisation detection of atoms, and that even with rather high levels of experimental imperfections, a reasonable amount of superadditivity can still be seen. To date, these types of measurement have only been realized on photons. It would be of great interest to have realizations using other physical systems. This is for fundamental reasons, but also since quantum coding gain in general increases with code word length, and a realization using atoms could be more easily scaled than existing realizations using photons.Comment: 10 pages, 5 figure

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“…The detector efficiency of field ionization detectors used in micromaser systems is ∼ 40% [35]. Improving both the efficiency of collection of electrons from ionized Rydberg states and the discrimination between Rydberg states prior to ionization is the subject of ongoing research [41], and we are confident that the necessary detector efficiencies are attainable.…”

Section: Implementation With Cavity Qedmentioning

confidence: 99%

Creating and observingN-partite entanglement with atoms

Everitt

¹

,

Jones

²

,

Varcoe

³

et al. 2011

J. Phys. B: At. Mol. Opt. Phys.

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A genuinely N-partite entangled state may display vanishing N-partite correlations measured for arbitrary local observables. In such states the genuine entanglement is noticeable solely in correlations between subsets of particles. A straightforward way to obtain such states for odd N is to design an 'anti-state' in which all correlations between an odd number of observers are exactly opposite. Evenly mixing a state with its anti-state then produces a mixed state with no N-partite correlations, with many of them genuinely multiparty entangled. Intriguingly, all known examples of 'entanglement without correlations' involve an odd number of particles. Here we further develop the idea of anti-states, thereby shedding light on the different properties of even and odd particle systems. We conjecture that there is no anti-state to any pure even-N-party entangled state making the simple construction scheme unfeasable. However, as we prove by construction, higher-rank examples of 'entanglement without correlations' for arbitrary even N indeed exist. These classes of states exhibit genuine entanglement and even violate an N-partite Bell inequality, clearly demonstrating the non-classical features of these states as well as showing their applicability for quantum communication complexity tasks. PACS numbers: 03.65.Ud Quantum entanglement is present in quantum states that cannot be obtained from uncorrelated states by local operations and classical communication [1, 2]. It turns out that for pure states the existence of entangle-ment is fully captured by N-partite correlation functions only: A pure state is entangled if and only if the sum of squared N-partite correlation functions exceeds certain bound [3-7]. One may then wonder if similar detection methods could exist for mixed states, i.e. whether appropriate processing of only N-partite correlation functions detects entanglement in all mixed states. The states we consider here demonstrate vividly that such a universal entanglement criterion does not exist. Despite vanishing N-partite correlation functions in all possible local measurements , these states can be even genuinely N-partite entangled. As a matter of fact the genuine N-partite en-tanglement is due to non-vanishing correlations between less than N particles, so-called lower order correlations. The first example of such a state was given in [8] and consists of an even mixture of two W states between an odd number of qubits. The two states have exactly opposite N-partite correlations such that they average out in the even mixture. More recently it was shown that any pure quantum state has an 'anti-state' where all correlation functions have opposite signs, but only between an odd number of observers [9, 10]. Then, the equal mixture of a pure state with odd number of qubits and its anti-state produces a mixed state with vanishing N-partite correlation functions. Many of such 'no-correlation' states are genuinely N-partite entangled and even an infinite family of such states with two continuous parameters could b...

show abstract

“…A final projective measurement which determines the energy level of the atom would be required. This is commonly done by means of field-ionisation detection [30,31], which involves passing the Rydberg atoms through an increasing electric field and measuring the energy at which the atom is ionised.…”

Section: Distinguishing Between Two Non-orthogonal Statesmentioning

confidence: 99%

Quantum Measurements of Atoms Using Cavity Qed

Dada

¹

,

Andersson

²

,

Jones

³

et al. 2011

International Conference on Quantum Information

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Generalized quantum measurements are an important extension of projective or von Neumann measurements, in that they can be used to describe any measurement that can be implemented on a quantum system. We describe how to realize two non-standard quantum measurements using cavity quantum electrodynamics (QED). The first measurement optimally and unabmiguously distinguishes between two non-orthogonal quantum states. The second example is a measurement that demonstrates superadditive quantum coding gain. The experimental tools used are single-atom unitary operations effected by Ramsey pulses and two-atom Tavis-Cummings interactions. We show how the superadditive quantum coding gain is affected by errors in the field-ionisation detection of atoms, and that even with rather high levels of experimental imperfections, a reasonable amount of superadditivity can still be seen. To date, these types of measurement have only been realized on photons. It would be of great interest to have realizations using other physical systems. This is for fundamental reasons, but also since quantum coding gain in general increases with code word length, and a realization using atoms could be more easily scaled than existing realizations using photons.

show abstract

Evolutionary optimization of state selective field ionization for quantum computing

Cited by 7 publications

References 12 publications

Quantum measurements of atoms using cavity QED

Quantum measurements of atoms using cavity QED

Creating and observingN-partite entanglement with atoms

Quantum Measurements of Atoms Using Cavity Qed

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