Joining the quantum state of two photons into one

Vitelli, Chiara; Spagnolo, Nicolò; Aparo, Lorenzo; Sciarrino, Fabio; Santamato, Enrico; Marrucci, Lorenzo

doi:10.1038/nphoton.2013.107

Cited by 75 publications

(77 citation statements)

References 30 publications

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“…For optical communication, this can be achieved either by increasing the number of transmitted photons, and/or by transmitting more than one bit (or qubit) per photon, i. e. encoding in an enlarged communication 'alphabet.' The latter corresponds to an increase in the number of orthogonal modes in which data is encoded [1]. Complex images can be used as one such set of orthogonal modes and have been shown to be highly efficient in storing data [2,3].…”

Section: Introductionmentioning

confidence: 99%

High speed switching between arbitrary spatial light profiles

Radwell¹,

Brickus²,

Clark³

et al. 2014

Opt. Express

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Complex images, inscribed into the spatial profile of a laser beam or even a single photon, offer a highly efficient method of data encoding. Here we present a prototype system which can quickly modulate between arbitrary images. We display an array of holograms, each defined by its phase and intensity profile, on a spatial light modulator. The input beam is then steered by an acousto-optic modulator to one of these holograms, where it is converted into the desired light mode. We demonstrate switching between characters within three separate alphabets at a switching rate of up to10 kHz. This rate is limited by our detection system, and we anticipate that the system is capable of far higher rates. Furthermore our system is not limited in efficiency by channel number, making it ideal for quantum communication applications.

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Section: Introductionmentioning

confidence: 99%

High speed switching between arbitrary spatial light profiles

Radwell¹,

Brickus²,

Clark³

et al. 2014

Opt. Express

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show abstract

“…We utilize time-correlated photon pairs generated in the process of spontaneous parametric downconversion in a nonlinear crystal pumped by a laser diode. The two signal qubits are encoded into the spatial and polarization degrees of freedom of the signal photon [24][25][26][27], respectively, while the auxiliary qubit is represented by polarization state of the idler photon [13,27]. The spatial qubit is supported by an inherently stable Mach-Zehnder interferometer formed by two calcite beam-displacers BD which introduce a transversal spatial offset between vertically and horizontally polarized beam.…”

Section: Methodsmentioning

confidence: 99%

Experimental replication of single-qubit quantum phase gates

et al. 2016

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We experimentally demonstrate the underlying physical mechanism of the recently proposed protocol for superreplication of quantum phase gates [W. Dür, P. Sekatski, and M. Skotiniotis, Phys. Rev. Lett. 114, 120503 (2015)], which allows to produce up to N 2 high-fidelity replicas from N input copies in the limit of large N . Our implementation of 1 → 2 replication of the single-qubit phase gates is based on linear optics and qubits encoded into states of single photons. We employ the quantum Toffoli gate to imprint information about the structure of an input two-qubit state onto an auxiliary qubit, apply the replicated operation to the auxiliary qubit, and then disentangle the auxiliary qubit from the other qubits by a suitable quantum measurement. We characterize the replication protocol by full quantum process tomography and observe good agreement of the experimental results with theory.

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“…where the resulting state can be described as a four-dimensional state |ψ A of a single system A. Quantum joining can be applied to quantum systems containing multi-degrees of freedom and has been experimentally demonstrated with single photons' polarization and spatial degrees of freedom [121], see also the theoretical analysis and structure of quantum joining [122].…”

Section: Minimal Resources For Entanglement Detectionmentioning

confidence: 99%

Designing quantum information processing via structural physical approximation

Bae

2017

Rep. Prog. Phys.

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In quantum information processing it may be possible to have efficient computation and secure communication beyond the limitations of classical systems. In a fundamental point of view, however, evolution of quantum systems by the laws of quantum mechanics is more restrictive than classical systems, identified to a specific form of dynamics, that is, unitary transformations and, consequently, positive and completely positive maps to subsystems. This also characterizes classes of disallowed transformations on quantum systems, among which positive but not completely maps are of particular interest as they characterize entangled states, a general resource in quantum information processing. Structural physical approximation offers a systematic way of approximating those nonphysical maps, positive but not completely positive maps, with quantum channels. Since it has been proposed as a method of detecting entangled states, it has stimulated fundamental problems on classifications of positive maps and the structure of Hermitian operators and quantum states, as well as on quantum measurement such as quantum design in quantum information theory. It has developed efficient and feasible methods of directly detecting entangled states in practice, for which proof-of-principle experimental demonstrations have also been performed with photonic qubit states. Here, we present a comprehensive review on quantum information processing with structural physical approximations and the related progress. The review mainly focuses on properties of structural physical approximations and their applications toward practical information applications.

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Joining the quantum state of two photons into one

Cited by 75 publications

References 30 publications

High speed switching between arbitrary spatial light profiles

High speed switching between arbitrary spatial light profiles

Experimental replication of single-qubit quantum phase gates

Designing quantum information processing via structural physical approximation

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