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Propagating Quantum Microwaves: Dual-path State Reconstruction and Path Entanglement

E. P. Menzel

Published Jan 1, 2013• 1 citation
OpenAlex

Abstract

Propagating quantum microwaves are promising for quantum communication and information processing protocols. In this thesis, we reconstruct the state of quantum microwaves with the dual-path method based on a beam splitter, off-the-shelf linear amplifiers and cross-correlation signal recovery techniques. Furthermore, making use of non-classical squeezed states produced by a Josephson parametric amplifier, we generate and detect continuous-variable frequency-degenerate path entanglement.

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Propagating quantum microwaves are promising for quantum communication and information processing protocols. In this thesis, we reconstruct the state of quantum microwaves with the dual-path method based on a beam splitter, off-the-shelf linear amplifiers and cross-correlation signal recovery techniques. Furthermore, making use of non-classical squeezed states produced by a Josephson parametric amplifier, we generate and detect continuous-variable frequency-degenerate path entanglement.
We study quantum state tomography, entanglement detection and channel noise reconstruction of propagating quantum microwaves via dual-path methods. The presented schemes make use of the following key elements: propagation channels, beam splitters, linear amplifiers and field quadrature detectors. Remarkably, our methods are tolerant to the ubiquitous noise added to the signals by phase-insensitive microwave amplifiers. Furthermore, we analyse our techniques with numerical examples and experimental data, and compare them with the scheme developed in Eichler et al (2011 Phys. Rev. Lett. 106 220503; 2011 Phys. Rev. Lett. 107 113601), based on a single path. Our methods provide key toolbox components that may pave the way towards quantum microwave teleportation and communication protocols.
We study quantum state tomography, entanglement detection and channel noise reconstruction of propagating quantum microwaves via dual-path methods. The presented schemes make use of the following key elements: propagation channels, beam splitters, linear amplifiers and field quadrature detectors. Remarkably, our methods are tolerant to the ubiquitous noise added to the signals by phase-insensitive microwave amplifiers. Furthermore, we analyse our techniques with numerical examples and experimental data, and compare them with the scheme developed in Eichler et al (2011 Phys. Rev. Lett. 106 220503; 2011 Phys. Rev. Lett. 107 113601), based on a single path. Our methods provide key toolbox components that may pave the way towards quantum microwave teleportation and communication protocols.
Two-mode squeezing is a fascinating example of quantum entanglement manifested in cross-correlations of non-commuting observables between two subsystems. At the same time, these subsystems themselves may contain no quantum signatures in their self-correlations. These properties make two-mode squeezed (TMS) states an ideal resource for applications in quantum communication. Here, we generate propagating microwave TMS states by a beam splitter distributing single mode squeezing emitted from distinct Josephson parametric amplifiers along two output paths. We experimentally study the fundamental dephasing process of quantum cross-correlations in continuous-variable propagating TMS microwave states and accurately describe it with a theory model. In this way, we gain the insight into finite-time entanglement limits and predict high fidelities for benchmark quantum communication protocols such as remote state preparation and quantum teleportation.
Two-mode squeezing is a fascinating example of quantum entanglement manifested in cross-correlations of non-commuting observables between two subsystems. At the same time, these subsystems themselves may contain no quantum signatures in their self-correlations. These properties make two-mode squeezed (TMS) states an ideal resource for applications in quantum communication. Here, we generate propagating microwave TMS states by a beam splitter distributing single mode squeezing emitted from distinct Josephson parametric amplifiers along two output paths. We experimentally study the fundamental dephasing process of quantum cross-correlations in continuous-variable propagating TMS microwave states and accurately describe it with a theory model. In this way, we gain the insight into finite-time entanglement limits and predict high fidelities for benchmark quantum communication protocols such as remote state preparation and quantum teleportation.
Path entanglement constitutes an essential resource in quantum information and communication protocols. Here, we demonstrate frequency-degenerate entanglement between continuous-variable quantum microwaves propagating along two spatially separated paths. We combine a squeezed and a vacuum state using a microwave beam splitter. Via correlation measurements, we detect and quantify the path entanglement contained in the beam splitter output state. Our experiments open the avenue to quantum teleportation, quantum communication, or quantum radar with continuous variables at microwave frequencies.
Propagating quantum microwaves are a key ingredient for quantum communication.A particular form of such quantum microwaves is squeezed states.In this work, we investigate squeezed states generated by Josephson parametric amplifiers (JPAs) with a dual-path setup.Squeezed coherent states can be generated by sending coherent states into a JPA.Alternatively, displacement operations can be performed using a directional coupler.We discuss our results in the context of remote state preparation and quantum teleportation. KurzzusammenfassungPropagierende Quantenmikrowellen sind Schlüsselbausteine für die Quantenkommunikation. Wir untersuchen gequetschte Zustände, die mit Josephson parametrischen Verstärkern (JPA) erzeugt werden, mit der Zweipfadmethode zur Zustandsrekonstruktion. Gequetschte kohärente Zustände können sowohl durch Einsenden eines kohärenten Signals in den JPA, als auch durch Anwenden einer Verschiebungsoperation auf einen gequestschten Vakuumzustand, generiert werden.Wir diskutieren unsere Ergebnisse im Rahmen von ferngesteuerter Zustandspräparation und Quantenteleportation.