Observation of Measurement-Induced Entanglement and Quantum Trajectories of Remote Superconducting Qubits
Nicolas Roch, Mollie E. Schwartz, Felix Motzoi, Chris Macklin, Rajamani Vijay, Andrew Eddins, Alexander N. Korotkov, K. Birgitta Whaley, Mohan Sarovar, Irfan A. Siddiqi · Physical Review Letters · 2014
The creation of a quantum network requires the distribution of coherent information across macroscopic distances. We demonstrate the entanglement of two superconducting qubits, separated by more than a meter of coaxial cable, by designing a joint measurement that probabilistically projects onto an entangled state. By using a continuous measurement scheme, we are further able to observe single quantum trajectories of the joint two-qubit state, confirming the validity of the quantum Bayesian formalism for a cascaded system. Our results allow us to resolve the dynamics of continuous projection onto the entangled manifold, in quantitative agreement with theory.