Using Cryogenic CMOS Control Electronics to Enable a Two-Qubit Cross-Resonance Gate
Devin Underwood, Joseph Glick, Ken Inoue, D.J. Frank, John Timmerwilke, Emily Pritchett, Sudipto Chakraborty, Kevin Tien, Mark Yeck, John F. Bulzacchelli, Chris Baks, R. P. Robertazzi, Matthew J. Beck, Rajiv Joshi, Dorothy Wisnieff, Scott Lekuch, B. Gaucher, Daniel J. Friedman, Pat Rosno, Daniel Ramirez, Jeff Ruedinger
Abstract
Qubit control electronics composed of CMOS circuits are of critical interest for next-generation quantum computing systems. A CMOS-based application-specific integrated circuit (ASIC) fabricated in 14-nm fin field-effect transistor (FinFET) technology was used to generate and sequence qubit control wave forms and demonstrate a two-qubit cross-resonance gate between fixed-frequency transmons. The controller was thermally anchored to the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mi>T</a:mi><a:mo>=</a:mo><a:mn>4</a:mn></a:math> K stage of a dilution refrigerator and the measured power was 23 mW per qubit under active control. The chip generated single-side banded output frequencies between 4.5 and 5.5 GHz, with a maximum power output of <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:mo>−</d:mo><d:mn>18</d:mn></d:math> dBm. Randomized-benchmarking (RB) experiments revealed an average number of 1.71 instructions per Clifford (IPC) for single-qubit gates and 17.51 IPC for two-qubit gates. A single-qubit error per gate of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><g:msub><g:mi>ϵ</g:mi><g:mtext>1Q</g:mtext></g:msub><g:mo>=</g:mo><g:mn>8</g:mn><g:mo>×</g:mo><g:msup><g:mn>10</g:mn><g:mrow><g:mo>−</g:mo><g:mn>4</g:mn></g:mrow></g:msup></g:math> and a two-qubit error per gate of <j:math xmlns:j="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><j:msub><j:mi>ϵ</j:mi><j:mtext>2Q</j:mtext></j:msub><j:mo>=</j:mo><j:mn>1.4</j:mn><j:mo>×</j:mo><j:msup><j:mn>10</j:mn><j:mrow><j:mo>−</j:mo><j:mn>2</j:mn></j:mrow></j:msup></j:math> were shown. A drive-induced <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><m:mi>Z</m:mi></m:math> rotation was observed by way of a rotary-echo experiment; this observation is consistent with the expected qubit behavior given the measured excess local-oscillator (LO) leakage from the CMOS chip. The effect of spurious drive-induced <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><p:mi>Z</p:mi></p:math> errors was numerically evaluated with a two-qubit model Hamiltonian and shown to be in good agreement with the measured RB data. The modeling results suggest that the <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><s:mi>Z</s:mi></s:math> error varies linearly with the pulse amplitude. Published by the American Physical Society 2024