Abstract
In developing the global Quantum Internet, quantum communication with low-Earth-orbit satellites will play a pivotal role. Such communication will need to be two way: effective not only in the satellite-to-ground (downlink) channel but also in the ground-to-satellite channel (uplink). Given that losses on this latter channel are significantly larger relative to the former, techniques that can exploit the superior downlink to enhance quantum communication in the uplink should be explored. In this work we do just that - exploring how continuous variable entanglement in the form of two-mode squeezed vacuum (TMSV) states can be used to significantly enhance the fidelity of ground-to-satellite quantum-state transfer relative to direct uplink-transfer. More specifically, through detailed phase-screen simulations of beam evolution through turbulent atmospheres in both the downlink and uplink channels, we demonstrate how a TMSV teleportation channel created by the satellite can be used to dramatically improve the fidelity of uplink coherent-state transfer relative to direct transfer. We then show how this, in turn, leads to the uplink-transmission of a higher alphabet of coherent states. Additionally, we show how non-Gaussian operations acting on the received component of the TMSV state at the ground station can lead to even further enhancement. Since TMSV states can be readily produced in situ on a satellite platform and form a reliable teleportation channel for most quantum states, our work suggests future satellites forming part of the emerging Quantum Internet should be designed with uplink-communication via TMSV teleportation in mind.
Highlights
INTRODUCTIONQ UANTUM COMMUNICATIONS via low-Earth-orbit (LEO) represent a critical component of the so-called Quantum Internet — a new heterogeneous global communication system based on classical and quantum communication techniques whose information security will be underpinned by quantum protocols such as quantum key distribution (QKD)
Q UANTUM COMMUNICATIONS via low-Earth-orbit (LEO) represent a critical component of the so-called Quantum Internet — a new heterogeneous global communication system based on classical and quantum communication techniques whose information security will be underpinned by quantum protocols such as quantum key distribution (QKD).This new internet will be used as the backbone communication system inter-connecting future quantum computers via routed quantum information transfer
We expand previous analyses of the uplink and downlink channels by including the excess noise in each channel. This excess noise limits the accuracy of the quadrature measurements, effectively reducing the amount of transferred quantum information. (ii) Using these same simulations, we determine the fidelity of coherent state transfer through direct uplink transfer. (iii) We model the creation of a resource continuous variable (CV) teleportation channel in the downlink that is created by sending from the satellite one mode of an in situ produced two-mode squeezed vacuum (TMSV) state. (iv) We use that resource to determine the fidelity of coherent state transfer to the satellite via teleportation, quantifying the gain achieved over direct transfer. (v) we investigate a series of non-Gaussian operations that can be invoked on the received TMSV mode at the ground station as a means to further enhance uplink coherent-state transfer via teleportation
Summary
Q UANTUM COMMUNICATIONS via low-Earth-orbit (LEO) represent a critical component of the so-called Quantum Internet — a new heterogeneous global communication system based on classical and quantum communication techniques whose information security will be underpinned by quantum protocols such as quantum key distribution (QKD). Continuous variable (CV) quantum information, where the information is encoded in the quadratures of the electromagnetic field of optical states, is widely touted as perhaps a more promising candidate to transfer quantum information [8], [9] This is largely due to the relatively technical simplicity (and maturity) of the CV-enabled devices required to send, receive, and measure quantum signals, robustness against background noise, and the potential of the enlarged Hilbert space associated with CV systems to lead to enhanced communication throughput in practical settings.. (i) Through a series of detailed phase-screen simulations, we quantify the asymmetric losses experienced by the downlink and uplink channels of a LEO satellite in quantum communication with a terrestrial ground station.
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