High coherence and low cross-talk in a tileable 3D integrated superconducting circuit architecture

Abstract

We report high qubit coherence as well as low cross-talk and single-qubit gate errors in a superconducting circuit architecture that promises to be tileable to two-dimensional (2D) lattices of qubits. The architecture integrates an inductively shunted cavity enclosure into a design featuring nongalvanic out-of-plane control wiring and qubits and resonators fabricated on opposing sides of a substrate. The proof-of-principle device features four uncoupled transmon qubits and exhibits average energy relaxation times T 1 = 149(38) μs, pure echoed dephasing times T ϕ, e = 189(34) μs, and single-qubit gate fidelities F = 99.982(4)% as measured by simultaneous randomized benchmarking. The 3D integrated nature of the control wiring means that qubits will remain addressable as the architecture is tiled to form larger qubit lattices. Band structure simulations are used to predict that the tiled enclosure will still provide a clean electromagnetic environment to enclosed qubits at arbitrary scale.

The Quantum Socket and DemuXYZ-Based Gates with Superconducting Qubits

“…A different wiring technique based on coaxial cables hanging directly above a qubit chip has been demonstrated in the works of Refs. [11,12]. Like the quantum socket, this interconnect is truly vertical and, thus, is potentially more scalable than current flip-chip techniques.…”

“…It is worth noting that, besides the quantum socket, only one other truly vertical interconnect has been proposed and char-acterized, as shown in the works of Refs. [11,12]. While spatial demultiplexing has been proposed in the work of Ref.…”

Unimon qubit

“…Currently, most of the superconducting multi-qubit processors utilize transmon qubits 1 , 17 , 24 , 25 that can be reproducibly fabricated 24 and have coherence times up to several hundred microseconds 26 , 27 , leading to record average gate fidelities of 99.98–99.99% for single-qubit gates 28 , 29 and 99.8–99.9% for two-qubit gates 30 , 31 . The transmon was derived from the charge qubit 32 by adding a shunt capacitor in parallel with a Josephson junction, with the result of exponentially suppressing the susceptibility of its transition frequency to charge noise.…”

“…15, 16. Despite the recent major developments in implementing distance-2-5 surface codes on superconducting quantum processors [17][18][19][20][21][22][23] , the gate and readout fidelities of superconducting qubits need to be improved further, preferably above 99.99%, to enable efficient quantum error correction with a reasonable qubit count.Currently, most of the superconducting multi-qubit processors utilize transmon qubits 1,17,24,25 that can be reproducibly fabricated 24 and have coherence times up to several hundred microseconds 26,27 , leading to record average gate fidelities of 99.98-99.99% for single-qubit gates 28,29 and 99.8-99.9% for two-qubit gates 30,31 . The transmon was derived from the charge qubit 32 by adding a shunt capacitor in parallel…”

Efficient qutrit gate-set tomography on a transmon

“…The qutrit characterized in this letter is a single superconducting transmon implemented in a 3D-integrated coaxial circuit design [39,40]. A transmon is a multilevel quantum Duffing oscillator consisting of a Josephson junction and a shunting capacitance [14].…”