Quantum key distribution without a shared reference frame

Souza, C. E. R.; Borges, C. V. S.; Khoury, A. Z.; Huguenin, J. A. O.; Aolita, Leandro; Walborn, S. P.

doi:10.1103/physreva.77.032345

Cited by 125 publications

(84 citation statements)

References 19 publications

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“…In order to demonstrate the usefulness of the fractional phases for quantum information protocols, it will be crucial to investigate the phase evolution under local random unitary transformations. It is well known that two-qubit entangled states are robust against certain kinds of noise [44], what motivated an alignment free quantum cryptography protocol [45,46]. We shall leave the investigation of the fractional phases under noisy evolutions to a future contribution.…”

Section: Discussionmentioning

confidence: 99%

Topological phase structure of entangled qudits

Khoury¹,

Oxman²

2014

Phys. Rev. A

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We discuss the appearance of fractional topological phases on cyclic evolutions of entangled qudits. The original result reported in Phys. Rev. Lett. 106, 240503 (2011) is detailed and extended to qudits of different dimensions. The topological nature of the phase evolution and its restriction to fractional values are related to both the structure of the projective space of states and entanglement. For maximally entangled states of qudits with the same Hilbert space dimension, the fractional geometric phases are the only ones attainable under local SU(d) operations, an effect that can be experimentally observed through conditional interference.

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Section: Discussionmentioning

confidence: 99%

Topological phase structure of entangled qudits

Khoury¹,

Oxman²

2014

Phys. Rev. A

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“…At first glance, this resistance offered by entangled states may look reminiscent of the robustness offered by entangled states against misaligned reference frames [18][19][20]. However, since a misaligned measurement, as explained in Sec.…”

Section: Two-qubit-entangled Statesmentioning

confidence: 99%

“…Note that the misalignment errors considered above include not only misalignments of the reference frame [18][19][20], but also nonunitary transformations that change the orthogonality relations between measurements axes, e.g., as in the example studied in Fig. 2.…”

Section: Misaligned Bases From Imperfect Measurementsmentioning

confidence: 99%

Imperfect measurement settings: Implications for quantum state tomography and entanglement witnesses

et al. 2012

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Reliable and well-characterized quantum resources are indispensable ingredients in quantum information processing. Typically, in a realistic characterization of these resources, apparatuses come with intrinsic uncertainties that can manifest themselves in the form of systematic errors. While systematic errors are generally accounted for through careful calibration, the effect of remaining imperfections on the characterization of quantum resources has been largely overlooked in the literature. In this paper, we investigate the effect of systematic errors that arise from imperfect alignment of measurement bases-an error that can conceivably take place due to the limited controllability of measurement devices. We show that characterization of quantum resources using quantum state tomography or entanglement witnesses can be undermined with an amount of such imprecision that is not uncommon in laboratories. Curiously, for quantum state tomography, we find that having entanglement can help to reduce the susceptibility to this kind of error. We also briefly discuss how a given entanglement witness can be modified to incorporate the effect of such errors.

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“…In these protocols individual photons must be carefully prepared in two distinct optical modes such as, e.g., TE (transverse electric) or TM (transverse magnetic) polarization modes [4] and HG 01 or HG 10 (Hermite-Gaussian) spatial modes [5], in order to implement bona fide qubits. Arbitrary mode control of a single photon has recently been demonstrated for the photon's amplitude [6][7][8][9][10], polarization [11], frequency [12] and phase [13].…”

Section: Introductionmentioning

confidence: 99%

All photons are equal but some photons are more equal than others

Töppel

Aiello

Leuchs

2013

2013 Conference on Lasers and Electro-Optics Pacific Rim (CLEOPR)

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Abstract. Two photons are said to be identical if they are prepared in the same quantum state. Given the latter, there is a unique way to achieve this. Conversely, there are many different ways of preparing two non-identical photons: they may differ in frequency, polarization, amplitude, etc. Therefore, photon distinguishability depends upon the specific degree of freedom being varied. By means of a careful analysis of the coincidence probability distribution in a Hong-Ou-Mandel experiment, we can show that photon distinguishability can be actually quantified by the rate of distinguishability of photons, an experimentally measurable parameter that crucially depends on both the photon quantum state and the degree of freedom under control.

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Quantum key distribution without a shared reference frame

Abstract: We report a simple quantum-key-distribution experiment in which Alice and Bob do not need to share a common polarization direction in order to send information. Logical qubits are encoded into nonseparable states of polarization and first-order transverse spatial modes of the same photon.

Cited by 125 publications

References 19 publications

Topological phase structure of entangled qudits

Topological phase structure of entangled qudits

Imperfect measurement settings: Implications for quantum state tomography and entanglement witnesses

All photons are equal but some photons are more equal than others

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