Superconducting Qubit Arrays for Quantum Logic Circuits
Jared Hertzberg IBM
Host: Matt LaHaye | Contact: Yudaisy Salomon Sargenton, email@example.com
Quantum computing holds the promise of exploiting superposition and entanglement to surpass conventional digital logic in certain classes of problems. Superconducting qubit circuits at millikelvin temperatures have recently demonstrated key advances such as robust and simple multi-qubit gates, the integration of superconducting qubits into arrays of four or more, and gate fidelities reaching 99%. [1,2,3] The technology has thus matured to the point of integrating multiple qubits to form functional quantum logic circuits. Such circuits will enable quantum error correction via the ‘surface code’ or similar algorithms. In this talk I will discuss a multi-qubit architecture under development at IBM Research, in which two-dimensional arrays of fixed-frequency transmon qubits are coupled via microwave-waveguide buses and microwave-driven two-qubit gates. To scale this architecture into a fully fault-tolerant quantum logic circuit will require advances in the basic physics, engineering and operation of these devices.  I will survey these challenges and focus in particular on two issues: 1) how to precisely allocate qubit frequencies in the vicinity of 5 GHz; and 2) how to rapidly read out the qubit state while minimizing losses via the Purcell effect. 
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 N. T. Bronn et al, Appl Phys Lett 107, 172601 (2015).