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Electro-optic control of quantum measurementsBuchler, Benjamin Caird. January 2001 (has links)
No description available.
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Competition between weak quantum measurement and many-body dynamics in ultracold bosonic gasesKozlowski, Wojciech January 2016 (has links)
Trapping ultracold atoms in optical lattices enabled the study of strongly correlated phenomena in an environment that is far more controllable and tunable than what was possible in condensed matter. Here, we consider coupling these systems to quantised light where the quantum nature of both the optical and matter fields play equally important roles in order to push the boundaries of what is possible in ultracold atomic systems. We show that light can serve as a nondestructive probe of the quantum state of matter. By considering a global measurement we show that it is possible to distinguish a highly delocalised phase like a superfluid from the Bose glass and Mott insulator. We also demonstrate that light scattering reveals not only density correlations, but also matter-field interference. By taking into account the effect of measurement backaction we show that the measurement can efficiently compete with the local atomic dynamics of the quantum gas. This can generate long-range correlations and entanglement which in turn leads to macroscopic multimode oscillations across the whole lattice when the measurement is weak and correlated tunnelling, as well as selective suppression and enhancement of dynamical processes beyond the projective limit of the quantum Zeno effect in the strong measurement regime. We also consider quantum measurement backaction due to the measurement of matter-phase-related variables such as global phase coherence. We show how this unconventional approach opens up new opportunities to affect system evolution and demonstrate how this can lead to a new class of measurement projections thus extending the measurement postulate for the case of strong competition with the system's own evolution.
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TOWARD QUANTUM NETWORKING WITH FREQUENCY-BIN QUDITS ON INTEGRATED PLATFORMSKarthik Vijay Annur Myilswamy (19797960) 03 October 2024 (has links)
<p dir="ltr">Quantum networking holds tremendous promise in transforming computation and communication. While matter-based systems excel as memory nodes, photons are ideal for long-distance transmission. Hence, a hybrid network combining both becomes essential. Moreover, developing entangled photon pair sources is critical for quantum repeaters and network implementation. The realization of these capabilities on integrated photonic circuits is vital for miniaturization and scalability. In this dissertation, we focus on two key aspects: establishing efficient photon-to-memory interfaces and generating and manipulating entangled states within integrated platforms.</p><p dir="ltr">One research direction involves developing an efficient interface between photons and matter-based memory, requiring spectral and temporal mode matching. Spectral compression is inevitable to realize low-loss interconnection between intrinsically narrowband memories and broadband photons. We proposed a novel approach using electro-optic time-varying cavities for spectral compression. Currently, we are working toward realizing this approach on the thin film lithium niobate platform.</p><p dir="ltr">In the other research focus, we encode quantum information as a coherent superposition of multiple optical frequencies; this approach is favorable due to its simplicity in generating high-dimensional entanglement and compatibility with fiber transmission. We successfully generated and reconstructed the density matrix of biphoton frequency combs from integrated silicon nitride microrings, achieving an 8x8 two-qudit dimensionality, the highest to date for frequency-bin qudits. Moreover, we employ Vernier electro-optic phase modulation methods to perform time-resolved measurements of biphoton correlation functions. Currently, we are exploring bidirectional pumping of microrings to generate indistinguishable entangled pairs in both directions, aiming to demonstrate key networking operations such as entanglement swapping and GHZ state generation in the frequency domain. We are also pursuing bidirectional pumping in a Sagnac configuration to generate simultaneous entanglement in both polarization and frequency, with the goal of deployment in a wavelength-multiplexed</p><p dir="ltr">network.</p>
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