Together with our academic collaborators, we've successfully executed large-scale algorithms on an error-corrected quantum computer with 48 logical qubits. This breakthrough, larger by orders of magnitude than any previous demonstration, marks a new era in scalable, fault-tolerant quantum computing - it signifies the transition from the era of physical qubits to the era of logical error-corrected qubits.
Quantum computers have the potential to solve complex problems in various fields, but noise affecting qubits has been a major hurdle, corrupting the computation before one can get the desired results. These errors can be fixed by combining several physical qubits to represent a single "logical" qubit. This process, called “quantum error correction”, makes the calculations more stable and reliable. With a sufficient number of error-corrected logical qubits, quantum computers can live up to their tremendous promise.
Our work leverages quantum error correction to enhance computation stability and reliability, solving the error problem. We've achieved quantum computation with 48 logical qubits and hundreds of entangling operations. This is a significant leap from previous demonstrations which showcased only to two logical qubits and one entangling gate. Moreover, we show that we can operate our logical qubits with a fidelity better than the component physical qubits. Impressively, this fidelity improves as we increase the code distance.
The research is the first to show large-scale algorithm execution on an error-corrected quantum computer. It opens the door to quantum devices capable of executing complex computations reliably, unveiling the technology's vast potential.
Previous experiments have been limited to one or two logical qubits. They could only correct a limited number of errors, constrained by small code distances. Our work significantly pushes these boundaries, not only increasing the number of logical qubits to 48 but also extending the code distance up to seven with better error suppression, thus offering more robust error correction capabilities.
This breakthrough is the culmination of many years of research and development in neutral-atom technology. The key developments that made this possible are:
Perhaps, but it's more difficult.
Our approach stands in contrast to superconducting machines, where several high-performance control lines are typically required for each physical qubit. As such, controlling 280 physical qubits in a superconducting quantum computer would require many hundreds of control signals, as opposed to fewer than 10 controls that we use here. Therefore, it will likely be challenging for other modalities to replicate this soon. To draw an analogy, it's akin to opening your 4K television and finding a dedicated wire for every pixel - clearly impractical. Our approach, on the other hand, allows for an increase in qubits without a proportional rise in control signals, greatly enhancing scalability.
Comparatively, qubits in ion trap quantum computers can be moved, but with limited parallelism.
Of course, neutral atom computers also have limitations, and we'll be happy to discuss them with interested parties.
The question of the requisite number of logical qubits for a truly-useful quantum computer remains a vibrant area of research, eliciting diverse opinions.
Some researchers posit that industrial applications would require quantum computers equipped with thousands of high-quality logical qubits. Conversely, others argue that merely 100 high-quality logical qubits could suffice, provided they are paired with optimized algorithms. Notably, such 100-qubit systems would eclipse the simulation capabilities of classical computers, which are limited to around 50 qubits. In our research, we intentionally capped our logical qubit count at 48. This allowed us to juxtapose our quantum system's results with simulated outcomes, affirming their authenticity.