arXiv subjects

Lorena Rebón

Publications and source records attributed to Lorena Rebón.

21 records · Page 2Linked to original sources

arXiv2019

A set of $4d-3$ observables to determine any pure qudit state

We present a tomographic method which requires only $4d-3$ measurement outcomes to reconstruct \emph{any} pure quantum state of arbitrary dimension $d$. Using the proposed scheme we have experimentally reconstructed a large number of pure states of dimension $d=7$, obtaining a mean fidelity of $0.94$. Moreover, we performed numerical simulations of the reconstruction process, verifying the feasibility of the method for higher dimensions. In addition, the \emph{a priori} assumption of purity can be certified within the same set of measurements, what represents an improvement with respect to other similar methods and contributes to answer the question of how many observables are needed to uniquely determine any pure state.

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arXiv2018

Characterizing $d-$dimensional quantum channels by means of quantum process tomography

In this work we propose a simple optical architecture, based on phase-only programmable spatial light modulators, in order to characterize general processes on photonic spatial quantum systems in a $d>2$ Hilbert space. We demonstrate the full reconstruction of typical noises affecting quantum computing, as amplitude shifts, phase shifts, and depolarizing channel in dimension $d=5$. We have also reconstructed simulated atmospheric turbulences affecting a free-space transmission of qudits in dimension $d=4$. In each case, quantum process tomography (QPT) was performed in order to obtain the matrix $χ$ that fully describe the corresponding quantum channel, $\mathcal{E}$. Fidelities between the states experimentally obtained after go through the channel and the expected ones are above $97\%$.

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arXiv2017

Determination of any pure spatial qudits from a minimum number of measurements by phase stepping interferometry

We present a proof-of-principle demonstration of a method to characterize \textit{any} pure spatial qudit of arbitrary dimension $d$, which is based on the classic phase shift interferometry technique. In the proposed scheme a total of only $4 d$ measurement outcomes are needed, implying a significant reduction with respect to the standard schemes for quantum state tomography which require of the order of $d^2$. By using this technique, we have experimentally reconstructed a large number of states ranging from $d=2$ up to $14$ with mean fidelity values higher than $0.97$. For that purpose the qudits were codified in the discretized transverse momentum-position of single photons, once they are sent through an aperture with $d$ slits. We provide an experimental implementation of the method based in a Mach-Zehnder interferometer, which allows to reduce the number of measurement settings to 4 since the $d$ slits can be measured simultaneously. Furthermore, it can be adapted to consider the reconstruction of the unknown state from the outcome frequencies of $4d-3$ fixed projectors independently of the encoding or the nature of the quantum system, allowing to implement the reconstruction method in a general experiment.

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