KEY HIGHLIGHTS
- Quantum Spin-Glass Discovery: Cornell researchers found a quantum spin-glass state in quantum algorithms, combining disorder and rigidity in qubits.
- Random Algorithms Unveil Secrets: The team studied random algorithms, revealing hidden spin-glass order and aiming to develop a new taxonomy of quantum states.
- Automatic Information Protection: The quantum spin-glass state implies automatic protection for certain types of information in quantum algorithms.
- Advancements in Error Correction: The study contributes to quantum error correction, proposing subsystem codes with multiple codewords for effective error detection and correction.
- Redundancy in Quantum Subsystem Codes: Quantum subsystem codes, using redundancy in storing information, simplify error detection and correction processes for qubits.
- Exploring Hidden Information: The researchers uncovered nontrivial structures, particularly the existence of spin-glass order, suggesting the presence of extra hidden information with potential use in quantum computing.
Cornell Scientists found a quantum spin-glass state in quantum algorithms, combining disorder and rigidity in qubits. At the microscopic level, window glass has some interesting properties. The atoms in it are all jumbled up like in a liquid, but they’re also stiff like in a solid. When you push or pull on one atom, it affects all the others.
Scientists use this idea to talk about a quantum state called a “quantum spin-glass.” In this state, the bits of quantum information in a quantum computer (called qubits) show both disorder, where they seem to take random values, and rigidity, meaning when one qubit changes, all the others do too. A group of researchers at Cornell stumbled upon this quantum state while studying quantum algorithms and ways to fix mistakes in quantum computing.
“Measuring the position of a quantum particle changes its momentum and vice versa. Similarly, for qubits, there are quantities that change one another when they are measured. We find that certain random sequences of these incompatible measurements lead to the formation of a quantum spin-glass,” said Erich Mueller, a physics professor at the College of Arts and Sciences at Cornell. “One implication of our work is that some types of information are automatically protected in quantum algorithms which share the features of our model.”
Recent Findings by Cornell Scientists
This research was recently published in Physical Review B, with Vaibhav Sharma, a physics doctoral student, as the lead author. Chao-Ming Jian, an assistant professor of physics, and Erich Mueller, the physics professor, also contributed as co-authors. They conducted their research at Cornell’s Laboratory of Atomic and Solid State Physics (LASSP), with funding from a College of Arts and Sciences New Frontier Grant.
“We are trying to understand generic features of quantum algorithms – features which transcend any particular algorithm. Our strategy for revealing these universal features was to study random algorithms. We discovered that certain classes of algorithms lead to hidden ‘spin-glass’ order. We are now searching for other forms of hidden order and think that this will lead us to a new taxonomy of quantum states,” said Vaibhav Sharma, the lead author and doctoral student in physics.
Random algorithms are those that incorporate a degree of randomness as part of the algorithm, like using random numbers to decide what to do next.
Advancements in Quantum Error Correction
Mueller’s 2021 New Frontier Grant proposal, titled “Autonomous Quantum Subsystem Error Correction,” aimed to make quantum computer designs simpler. The goal was to create a new method to fix errors in quantum processors caused by things like cosmic rays or magnetic fields, which can interfere with the qubits, messing up the information.
Mueller explained that classical computers protect their bits with error-correcting codes. This means that information is duplicated, so if one bit has an issue, you can spot it and correct the error. Mueller emphasized the need to find similar ways to protect qubits for quantum computing to be practical now and in the future.
Mueller stressed the importance of redundancy in error correction. “The key to error correction is redundancy. If I send three copies of a bit, you can tell if there is an error by comparing the bits with one another. We borrow language from cryptography for talking about such strategies and refer to the repeated set of bits as a ‘codeword.’”
In their research on spin-glass order, Mueller and his team explored a generalization where multiple codewords represent the same information. In a subsystem code, for instance, the bit “1” could be stored in four different ways: 111, 100, 101, and 001.
“The extra freedom that one has in quantum subsystem codes simplifies the process of detecting and correcting errors,” Mueller said.
The researchers clarified that their goal wasn’t just to create a better error protection system. Instead, they were studying random algorithms to understand general properties. Mueller noted, “Interestingly, we found nontrivial structure. The most dramatic was the existence of this spin-glass order, which points toward there being some extra hidden information floating around, which should be useable in some way for computing, though we don’t know how yet.”
Reference: “Subsystem symmetry, spin-glass order, and criticality from random measurements in a two-dimensional Bacon-Shor circuit” by Vaibhav Sharma, Chao-Ming Jian and Erich J. Mueller, 31 July 2023, Physical Review B. DOI: 10.1103/PhysRevB.108.024205
Source(s): SciTechDaily
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