arXiv subjects

Isabelle Herbauts

Publications and source records attributed to Isabelle Herbauts.

5 recordsLinked to original sources

arXiv2015

Secret Sharing with a Single d-level Quantum System

We give an example of a wide class of problems for which quantum information protocols based on multi-system entanglement can be mapped into much simpler ones involving one system. Secret sharing is a cryptographic primitive which plays a central role in various secure multiparty computation tasks and management of keys in cryptography. In secret sharing protocols, a classical message is divided into shares given to recipient parties in such a way that some number of parties need to collaborate in order to reconstruct the message. Quantum protocols for the task commonly rely on multi-partite GHZ entanglement. We present a multiparty secret sharing protocol which requires only sequential communication of a single quantum d-level system (for any prime d). It has huge advantages in scalabilility and can be realized with the state of the art technology. n be realized with the state of the art technology.

quant-ph↗

arXiv2013

Experimental implementation of a Kochen-Specker set of quantum tests

The conflict between classical and quantum physics can be identified through a series of yes-no tests on quantum systems, without it being necessary that these systems be in special quantum states. Kochen-Specker (KS) sets of yes-no tests have this property and provide a quantum-versus-classical advantage that is free of the initialization problem that affects some quantum computers. Here, we report the first experimental implementation of a complete KS set that consists of 18 yes-no tests on four-dimensional quantum systems and show how to use the KS set to obtain a state-independent quantum advantage. We first demonstrate the unique power of this KS set for solving a task while avoiding the problem of state initialization. Such a demonstration is done by showing that, for 28 different quantum states encoded in the orbital-angular-momentum and polarization degrees of freedom of single photons, the KS set provides an impossible-to-beat solution. In a second experiment, we generate maximally contextual quantum correlations by performing compatible sequential measurements of the polarization and path of single photons. In this case, state independence is demonstrated for 15 different initial states. Maximum contextuality and state independence follow from the fact that the sequences of measurements project any initial quantum state onto one of the KS set's eigenstates. Our results show that KS sets can be used for quantum-information processing and quantum computation and pave the way for future developments.

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arXiv2009

Photon bunching in parametric down-conversion with continuous wave excitation

The first direct measurement of photon bunching (g2 correlation function) in one output arm of a spontaneous-parametric-down-conversion source operated with a continuous pump laser in the single-photon regime is demonstrated. The result is in agreement with the statistics of a thermal field of the same coherence length, and shows the feasibility of investigating photon statistics with compact cw-pumped sources. Implications for entanglement-based quantum cryptography are discussed.

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arXiv2005

The Status of the Wave Function in Dynamical Collapse Models

The idea that in dynamical wave function collapse models the wave function is superfluous is investigated. Evidence is presented for the conjecture that, in a model of a field theory on a 1+1 lightcone lattice, knowing the field configuration on the lattice back to some time in the past, allows the wave function or quantum state at the present moment to be calculated, to arbitrary accuracy so long as enough of the past field configuration is known.

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arXiv2004

Simulating causal collapse models

We present simulations of causal dynamical collapse models of field theories on a 1+1 null lattice. We use our simulations to compare and contrast two possible interpretations of the models, one in which the field values are real and the other in which the state vector is real. We suggest that a procedure of coarse graining and renormalising the fundamental field can overcome its noisiness and argue that this coarse grained renormalised field will show interesting structure if the state vector does on the coarse grained scale.

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