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Quantum state characterization and state engineering using photon-number-resolving measurements
Rajveer Nehra - University of Virginia, Charlottesville, VA
Friday, February 28, 2020, 12:00-12:40 pm Calendar
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We are in the midst of a second quantum revolution fueled by the remarkable quantum mechanical properties of physical systems. Therefore, characterization and engineering of these quantum systems is vitally important in emerging quantum optical science and technology. The Wigner quasi-probability distribution function provides such a characterization. First, we present our recent results on quantum state tomography of a single-photon Fock state by photon-number-resolving (PNR) measurements using superconducting transition-edge sensor [1]. We directly probe the negativity of the Wigner function in our raw data without any inference or correction for decoherence, which is also an important indicator of the “quantum-only” nature of a physical system. Next, we introduce and experimentally demonstrate a state characterization protocol by measuring the Wigner function overlap between the unknown state and a sufficiently large set of readily available coherent state probes [2]. Unlike conventional continuous variable state tomography methods, our method utilizes computationally efficient semi-definite programming and can be used to accurately reconstruct the state even after loss a known loss. The protocol is demonstrated for a weak coherent state and a single-photon Fock state, and is shown to be robust to experimental noise. Towards the end, we discuss about ongoing experiment for generating non-Gaussian states using a process known as photon catalysis which involves coherent states, single-photon states, linear optics, and PNR measurements [3]. [1] R. Nehra et al., Optica 6,1356–1360 (2019). [2] R. Nehra et al., arXiv:1911.00173v1. [3] M. Eaton et al., N.J.Phys. 21, 113034 (2019). (pizza and drinks served at 12pm; talk starts at 12:10pm)

This talk is organized by Andrea F. Svejda