Abstract 16 December 2015

A Multi-Qubit Quantum Register Encoded in a Superconducting Cavity Resonator

Reinier Heeres, Yale University

In quantum information processing one usually thinks about two-level systems, or qubits, as the basic building blocks. A quantum register with a Hilbert-space size exponential in the number of qubits is then constructed using multiple two-level systems. Complex operations on the register are typically decomposed into elementary single- and two-qubit gates. In contrast to this, we study long-lived superconducting cavity resonators with an intrinsically large Hilbert space as an alternative building block. However, these come with the drawback of being linear systems with equally spaced energy levels, making it harder to manipulate them. In this talk I will show how we can interpret the cavity state as a multi-qubit register and how we perform quantum control mediated by a far off-resonantly coupled transmon qubit. In previous work we have demonstrated a constructive approach to manipulate the system [1], thus proving that it is controllable in principle. Here we resort to optimal control methods to realize arbitrary manipulations on the register on a significantly shorter time-scale of order 1/chi, the dispersive shift. In practice this results in shaped microwave pulses between one and two microseconds long. Our cavity-based multi-qubit register could function as the basic element in a networked quantum architecture.

[1] Heeres et al., Phys. Rev. Lett. 115, 137002 (2015)



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