arXiv subjects

Iris Agresti

Publications and source records attributed to Iris Agresti.

22 records · Page 2Linked to original sources

arXiv2018

Experimental device-independent tests of quantum channels

Quantum tomography is currently the mainly employed method to assess the information of a system and therefore plays a fundamental role when trying to characterize the action of a particular channel. Nonetheless, quantum tomography requires the trust that the devices used in the laboratory perform state generation and measurements correctly. This work is based on the theoretical framework for the device-independent inference of quantum channels that was recently developed and experimentally implemented with superconducting qubits in [Dall'Arno, Buscemi, Vedral, arXiv:1805.01159] and [Dall'Arno, Brandsen, Buscemi, PRSA 473, 20160721 (2017)]. Here, we present a complete experimental test on a photonic setup of two device-independent quantum channels falsification and characterization protocols to analyze, validate, and enhance the results obtained by conventional quantum process tomography. This framework has fundamental implications in quantum information processing and may also lead to the development of new methods removing the assumptions typically taken for granted in all the previous protocols.

quant-ph↗

arXiv2018

Device independent certification of a quantum delayed choice experiment

Wave-particle duality has long been considered a fundamental signature of the non-classical behavior of quantum phenomena, specially in a delayed choice experiment (DCE), where the experimental setup revealing either the particle or wave nature of the system is decided after the system has entered the apparatus. However, as counter-intuitive as it might seem, usual DCEs do have a simple causal explanation. Here, we take a different route and under a natural assumption about the dimensionality of the system under test, we present an experimental proof of the non-classicality of a DCE based on the violation of a dimension witness inequality. Our conclusion is reached in a device-independent and loophole-free manner, that is, based solely on the observed data and without the need on any assumptions about the measurement apparatus.

quant-ph↗

arXiv2017

Experimental learning of quantum states

The number of parameters describing a quantum state is well known to grow exponentially with the number of particles. This scaling clearly limits our ability to do tomography to systems with no more than a few qubits and has been used to argue against the universal validity of quantum mechanics itself. However, from a computational learning theory perspective, it can be shown that, in a probabilistic setting, quantum states can be approximately learned using only a linear number of measurements. Here we experimentally demonstrate this linear scaling in optical systems with up to 6 qubits. Our results highlight the power of computational learning theory to investigate quantum information, provide the first experimental demonstration that quantum states can be "probably approximately learned" with access to a number of copies of the state that scales linearly with the number of qubits, and pave the way to probing quantum states at new, larger scales.

quant-ph↗

arXiv2017

Tunable two-photon quantum interference of structured light

Structured photons are nowadays an interesting resource in classical and quantum optics due to the richness of properties they show under propagation, focusing and in their interaction with matter. Vectorial modes of light in particular, a class of modes where the polarization varies across the beam profile, have already been used in several areas ranging from microscopy to quantum information. One of the key ingredients needed to exploit the full potential of complex light in quantum domain is the control of quantum interference, a crucial resource in fields like quantum communication, sensing and metrology. Here we report a tunable photon-photon interference between vectorial modes of light. We demonstrate how a properly designed spin-orbit device can be used to control quantum interference between vectorial modes of light by simply adjusting the device parameters and no need of interferometric setups. We believe our result can find applications in fundamental research and quantum technologies based on structured light by providing a new tool to control quantum interference in a compact, efficient and robust way.

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