IMPANEMA: Improving Qubit Performance with Advanced, Novel, & Emerging Materials and Architectures
Abstract
The field of superconducting qubits (SQ) is rapidly progressing toward the realization of prototype error detection and quantum supremacy l- 3. To date, most demonstrations use the transmon qubit design4, in which a large (~70 fF) capacitor shunts a single or split-pair Josephson junction (JJ) to reduce charge noise sensitivity. Typically, qubit JJs are fabricated using two Aluminum (Al) electrodes separated by a thin (~1 nm) insulating and amorphous aluminum oxide (AIOx) tunneling barrier, forming an S-I-S junction. To make frequency-tunable qubits, such S-I-S JJs are embedded in a loop of superconducting material, e.g., a "split-pair" SQUID configuration. Applying a magnetic field to the loop tunes the effective critical current of the JJs and, thereby, the qubit transition frequency. Together with resonant microwaves, this approach enables high-fidelity 1- and 2-qubit operations5, 6. Despite the tremendous success of the state-of-the-art S-I-S superconducting qubits, there remain certain limitations to scaling within this framework, including: 1. Reduced coherence due to noise sources local to the qubit and JJs, increasing the resources required for fault-tolerant computing; 2. Static, continual power dissipation due to the current (flux) bias of each qubit; 3. Cross-talk due to stray magnetic fields from flux-bias lines, the DC current used to bias the qubits, and return-current paths, exacerbating calibration requirements; 4. A need for both microwave generators and arbitrary waveform generators to control the qubits, leading to large resource requirements. In this proposal, we address these and related limitations by developing advanced, novel JJ and control technologies: ¥Work Package 1 (WP1) - voltage-tunable qubits: We will develop and implement a magnetic-field-free, frequency-tunable superconducting qubit. We do this by moving to a voltage-tunable Josephson junction (VT-JJ) comprising gate-tunable van der Waals materials and quantum wells in place of AIOx. In VT-JJ devices, the critical current (qubit frequency) is tuned by an electrostatic gate. ¥Work Package 2 (WP2) - control without microwaves: We will develop composite qubits and control schema that do not rely on external microwave generators to realize high-fidelity single and coupled qubit gates. These devices will be benchmarked using qubits with both conventional Al-AIOx-AI junctions and voltage-tunable junctions from WP1 as they mature.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 11, 2018
- Source ID
- W911NF1810116
Entities
People
- William D Oliver
Organizations
- Army Contracting Command
- Massachusetts Institute of Technology
- National Security Agency