Fluxonium-based quantum processors
Abstract
Despite enabling remarkable progress in the field of superconducting quantum computing, transmon qubits suffer from two profound limitations: (i) dielectric loss in the shunting capacitor limits the coherence time T2* to about 100-200 microsecond even with best materials. (ii) the anharmonicity of the qubit transition is limited to only 5% (300-400 MHz) due to the large value of the shunt required to protect from charge noise. The latter slows down 2-qubit gates by, e.g., by reducing dispersive shifts, enhancing the unwanted Kerr effect, and causing state leakage under strong irradiation. We propose to explore fluxoniums to overcome both limitations. Our recent experiments (within the ARO - HiPS program) demonstrated that fluxoniums can indeed attain superior to transmon characteristics, with demonstrated coherence time T2* > 1 ms AND single qubit gates fidelity over 0.9999. Many proposals for high-fidelity 2-qubit gates on fluxoniums have been put forward, and our first generation experiments demonstrated fidelity as high as 0.995 on rather sub-optimal devices. These demonstrations set the stage for pursuing coupled fluxonium systems of more than 2 qubits. The key objective of our proposal is to demonstrate high-fidelity two-qubit operations in 2+ coupled qubit devices with individual qubit control and readout. To meet this objective, we will in parallel explore various means to i) optimize further qubit circuit parameters and coherence, ii) understand and optimize the qubit QND readout, which is necessary for quantum error correction, iii) optimize to theoretical limit two-qubit gates in two-qubit devices and select the optimal gate scheme for scaling beyond 2 qubits, iv) explore and mitigate quantum cross-talk in 2+ qubit devices, including the readout cross-talk, and v) demonstrate elementary quantum error correction protocols arising from the superior properties of the fluxonium spectra. Our project involves a collaboration between 4 experimental groups (Manucharyan, Wang, Huard, Kou) with a broad range of expertise and a theory group (Vavilov) specializing on fluxoniums. As necessary for the main goal, we will fabricate multi-fluxonium devices in a broad range of parameters using advanced cleanroom facilities, design and optimize microwave packaging compatible with multi-fluxonium control, and apply standard gate error benchmarking techniques. If successful, our project will establish a new path for constructing multi-qubit processors with a reduced error rates
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 24, 2023
- Source ID
- W911NF2310093
Entities
People
- Vladimir E Manucharyan
Organizations
- Army Contracting Command
- National Security Agency
- Swiss Federal Institute of Technology in Lausanne