![]() The key question that the threshold theorem resolves is whether quantum computers in practice could perform long computations without succumbing to noise. These results built off a paper of Peter Shor, which proved a weaker version of the threshold theorem. This result was proven (for various error models) by the groups of Dorit Aharanov and Michael Ben-Or Emanuel Knill, Raymond Laflamme, and Wojciech Zurek and Alexei Kitaev independently. This shows that quantum computers can be made fault-tolerant, as an analogue to von Neumann's threshold theorem for classical computation. ![]() In quantum computing, the threshold theorem (or quantum fault-tolerance theorem) states that a quantum computer with a physical error rate below a certain threshold can, through application of quantum error correction schemes, suppress the logical error rate to arbitrarily low levels. We are essentially building really good components that will be used in a larger computation.Quantum error correction schemes can suppress the logical error rate arbitrarily low “You cannot really solve an industry-relevant problem with the number of logical qubits we are dealing with right now. “It is laying the groundwork,” Stutz said. He feels that researchers will be able to solve many practical problems once they scale systems to 50 logical qubits with lower error rates than physical qubits. ![]() Stutz says this research is a significant milestone on the long road to fault-tolerant quantum computing. “It is an exciting time for learning about quantum error correction.” “We are now testing quantum error correction code concepts dreamed up in the late 1990s and can implement in these real systems for the first time,” Stutz said. In many quantum architectures, each qubit is only connected to a few neighbors. Although the Quantinuum approach isn’t delivering as many raw physical qubits as other approaches, these are fully connected, which opens opportunities to leverage these innovative algorithms. Researchers have thought about how different quantum error correction approaches might work. Stutz said future work will explore ways to ensure they are not adding more errors than they remove with an error correction code. The simple act of probing a qubit for errors can introduce new ones. One remaining challenge is the quantum error correction cycle. Russell Stutz, director of commercial hardware at Quantinuum, told VentureBeat this means that as they add more qubits, the probability of getting failures that ruin the entire computation decreases with a modest rise in the number of physical qubits. They implemented this new color code technique on top of Quantinuum’s latest computer with 20 physical qubits to create two reliable logical qubits. These new logical qubits can be efficiently scaled in a way that increases fault tolerance that was not practical with the physical qubits or even the 5-qubit approach. In the new technique, called a color code, the researchers found a way to combine seven logical qubits into one logical qubit in coordination with 2-3 ancillary qubits used for probing. However, this still increased errors as the number of qubits was scaled. Last year, Quantinuum demonstrated a practical implementation of these techniques in a quantum computer using a 5-qubit code. Previous theoretical research identified a way to correct both types of errors by constructing logical qubits. In a bit flip error, the qubit flips the computational state incorrectly from zero to one and vice versa. In a phase flip error, which does not occur in a classical computer, the phase of the qubit flips state. ![]() Quantum computers can suffer from two kinds of errors: bit flips and phase flips. A relatively simple parity check in classical computing can produce new errors in quantum computing. There are more kinds of errors that need to be corrected. Quantum computing can introduce new problems. If an error occurs, the supervisory system can detect if the calculation does not match and can safely ignore it if it does not match the others. A supervisory system compares the results. Hardware errors in which a transistor spontaneously switches tend to be rare in modern semiconductor circuits, but in some cases - like running a safety-critical system exposed to radiation - engineers design error correction systems that combine three processors. This work will ultimately pave the way to build fault-tolerant quantum computers that can scale to address significant problems. ![]() Researchers commonly refer to the current generation of quantum computers as part of the noisy intermediate scale quantum (NISQ) era. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |