Superconducting Qubits for Robust Remote Entanglement via Adiabatic State Transfer*

Efficient quantum communication between remote quantum nodes relies on high fidelity quantum state transfer and entanglement generation. Loss in the communication channel connecting the quantum nodes can significantly limit the efficiency of these processes. One proposed method to overcome channel loss is to use adiabatic protocols to transfer quantum states without populating the lossy communication channel. Here we construct and operate a superconducting system to test such methods, using two superconducting qubits connected by a 0.73 m long transmission channel, where the channel loss can be externally varied over two orders of magnitude (as measured by the Q of the resonant channel modes). We demonstrate that in the limit of low loss, an adiabatic passage method performs as well as previously demonstrated relay method [1], while in the presence of strong loss, the adiabatic passage achieves states transfer and entanglement fidelities more than a factor of two larger than the relay method.
[1] Y. Zhong, et al., Nature Physics 15, 741 (2019).