Abstract
Communication over proven-secure quantum channels is potentially one of the most wide-ranging applications of currently developed quantum technologies. It is generally envisioned that in future quantum networks, separated nodes containing stationary solid-state or atomic qubits are connected via the exchange of optical photons over large distances. In this work we explore an intriguing alternative for quantum communication via all-microwave networks. To make this possible, we describe a general protocol for sending quantum states through thermal channels, even when the number of thermal photons in the channel is much larger than one. The protocol can be implemented with state-of-the-art superconducting circuits and enables the transfer of quantum states over distances of ~100 m via microwave transmission lines cooled to only T=4K. This opens up completely new possibilities for quantum communication within and across buildings, and consequently, for the implementation of intra-city quantum networks based on microwave technology only.
Highlights
Superconducting circuits [1,2,3] are considered one of the most promising platforms for implementing quantum information processing schemes, where all the key elements, like high-fidelity single- and two-qubit gates [4], efficient readout [5,6], and error-correction capabilities [7,8,9], have already been experimentally demonstrated
We describe a general protocol for sending quantum states through thermal channels, even when the number of thermal photons in the channel is much larger than 1
The key ingredient, namely, the use of an intermediary oscillator as a controllable port between the local qubit and the quantum communication channel, provides the necessary degree of linearity for a coherent cancellation of noise, it enables the implementation of protocols for correcting the residual photon loss and absorption errors under realistic conditions
Summary
Superconducting circuits [1,2,3] are considered one of the most promising platforms for implementing quantum information processing schemes, where all the key elements, like high-fidelity single- and two-qubit gates [4], efficient readout [5,6], and error-correction capabilities [7,8,9], have already been experimentally demonstrated. Superconducting qubits are usually operated at transition frequencies of a few GHz, which requires cooling of the circuits to a few tens of mK in order to avoid detrimental thermal excitations This restricts the generation of entanglement and the coherent exchange of quantum information to qubits and photons located within the same dilution refrigerator [10,11,12,13]. Our analysis shows that by using alreadyexisting superconducting circuit technology combined with realistically achievable loss rates in microwave transmission lines, a deterministic exchange of quantum information over tens and even hundreds of meters is possible At this threshold, communication across buildings and, the establishment of fully connected microwave.
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