Speaker: Anatoly Kulikov
Affiliation: ETH Zurich
Date: Thursday, 20 February 2025 at 12:00
Location: Seminar Room, Serrano 121 (CFMAC)
In ETH Zurich, we have assembled a primitive two-node superconducting circuit QED network consisting of two dilution cryostats connected into a 30m-long cryogenic quantum link. Performing a loophole-free Bell test with this system allowed us to gain access to the elusive resource of non-locality, and enabled implementing {\it device-independent} routines. In the first part of the talk, I will present device-independent self-testing and randonmess amplification protocols, which perform two tasks not attainable in classical information processing without extra assumptions: verifying correct operation of the communication network without trusting the constituent devices, and generating certified high-quality randomness without having prior access to perfect randomness. In the second part of the talk, I will show new experimental results based on the ongoing joint work with CSIC. We perform a bidirectional photon transfer protocol, where a microwave photon emitted by Alice’s communication qubit acquires a conditional phase based on the state of Bob’s qubit. We vary the communication photon frequency, hence tuning the conditional phase acquired during the reflection off the remote node, effectively implementing an arbitrary-phase CZ gate. We apply it to perform remote single-shot readout of a quantum bit in a network node located 30~m away, achieving single-shot readout fidelity exceeding 83%. An interesting feature of the scheme is that it requires neither precise synchronization between active node and the remote node, nor any active participation by the remote node.