Google Bristlecone: A New Quantum processor by Google’s Quantum AI lab

Google’s Bristlecone was unveiled at the annual American Physical Society meeting in Los Angeles on March 5, 2018. According to Google, “Bristlecone would be a compelling proof-of-principle for building larger scale quantum computers.” The purpose of this quantum processor is to provide a testbed for research into system error rates and scalability of Google’s qubit technology along with applications in quantum simulation, optimization, and machine learning.

A Preview of Bristlecone, Google’s New Quantum Processor. On the right, is a cartoon of the device: each “X” represents a qubit, with nearest neighbor connectivity.

Google Bristlecone uses a new architecture that allows 72 quantum bits on a single array with an overlapping design that puts two different grids together. Google has optimized Bristlecone for the lowest possible error rate using a specialized process called Quantum Error Correction. The previous 9-qubit linear quantum computers by Google demonstrated error rates of 1% readout, 0.1% single-qubit gates and 0.6% two-qubit gates. Google Bristlecone uses the same scheme for coupling, control, and readout, but is scaled to a square array of 72 qubits. Google researchers chose a device of this size to demonstrate quantum supremacy in the future, to investigate first and second order error-correction using the surface code, and to facilitate quantum algorithm development on actual hardware.

The intended research direction of the Quantum AI Lab is to access near-term applications on the road to building an error corrected quantum computer. For this, Google says, “would require harmony between a full stack of technology ranging from software and control electronics to the processor itself. Getting this right requires careful systems engineering over several iterations.”

More information about Google Bristlecone is available in the Google research blog.