Patricio Arrangoiz-Arriola and Earl Campbell, researchers at AWS today came out with the first architecture paper from the AWS quantum computing team. The paper discusses the possibility of quantum error corrections through the use of cat qubits.
“The paper outlines a way to build a large-scale processor based on cat qubits,” said the researchers on their blog post, while adding that “implementing quantum error correction at scale is a monumental scientific and engineering challenge.”
Existing quantum computing hardware is ridden with noise and hence is prone to errors. An error-corrected quantum computer, therefore, is central to the goal of executing complex quantum algorithms. And that in turn is a prerequisite to building scale and commercial viability for complex tasks using the power of quantum computing.
According to the AWS paper, titled “Building a fault-tolerant quantum computer using concatenated cat codes” it seems that it may be possible to pack in information efficiently to build a large-scale processor by using cat qubits.
The architecture described in the paper to build a fault-tolerant quantum computer combines elements of active and passive quantum error correction.
Cat states are quantum superpositions of coherent but opposite phase states. More than two decades ago in 1999, researchers in the quantum optics community pointed out that these states can be used to encode a qubit of information in an oscillator.
Nowadays, creating cat states in the lab is a routine task. Usually, researchers do this using microwave oscillators. However, imperfections in real hardware make these cat states unstable, causing them to decay and dephase.
The highly biased error rates of cat qubits based on superconducting circuits can be exploited when designing additional QEC. The AWS way to build a large-scale processor based on cat qubits has been substantiated by simulations which span from component level up to the system level.
The team was able to obtain realistic full-resource estimates of the physical error rates and overheads needed to run useful fault-tolerant quantum algorithms. And they concluded that “with around 1,000 superconducting circuit components, one could construct a fault-tolerant quantum computer that can run circuits which are intractable for classical supercomputers.”