![]() In the late 1990s, theoretical physicist Juan Maldacena, now at the Institute for Advanced Study in Princeton, NJ, proposed the " AdS/CFT correspondence," which mathematically maps some models of gravity onto gravity-free quantum field theories. In recent papers, Harlow and others showed that working correction schemes can be deduced from a surprising source: the analysis of quantum gravity. The challenge is to identify specific ways to efficiently entangle a set of qubits so the information is reliably preserved. "It’s almost like you have two copies–but not quite," said Harlow. Even though the outcome for each is intrinsically unpredictable, the two will always agree. Entanglement, called "spooky action at a distance" by Einstein, links the measured properties of two separated quantum systems, such as qubits. In these schemes, "the information is stored non-locally in the entanglement between the qubits," said Daniel Harlow, a post-doctoral researcher in the High Energy Theory Group of the Center for the Fundamental Laws of Nature at Harvard University. If the combination is chosen properly, then even if one of the qubits is disturbed, the combined state preserves the original information (just as 110, 101, and 111 still represent 1 for three classical bits). In the mid-1990s, however, researchers were able to show that quantum error correction could be achieved by spreading the quantum state among many qubits (without looking at them, which would destroy the quantum information). Quantum mechanics, however, forbids "cloning" of a quantum state, so physicists at first thought that error correction would be impossible for quantum computing, making it much less useful. Even if one of the bits is changed, invoking a majority rule will still give a reliably correct answer (at the cost of extra hardware to store the redundant bits). This problem could be solved in an ordinary computer by using an error-correcting code, such as redundantly representing 1 x 3 independent bits, 111. Unfortunately, the delicate quantum states can be disrupted by tiny changes in the environment, so even a carefully isolated system would not have time to complete a usefully complex calculation. Because each qubit can represent both 0 and 1 simultaneously, an assembly of them could in principle perform some massively parallel computations exponentially faster than an ordinary computer. ![]() Now, their attempt to reconcile quantum information and gravity has revealed a surprising connection: new types of error-correcting codes for proposed quantum computers have emerged from tools developed to study quantum gravity.įor decades, physicists have aspired to compute using quantum bits, or qubits, in place of the bits used by "classical" computers. Information seems abstract, but it plays surprisingly substantive roles in physics for example, trying to understand what happens to the information content of matter that falls into a black hole has forced theorists to question their views of relativity and quantum mechanics. Implementation of the surface code and other quantum error correction codes.New types of error-correcting codes for proposed quantum computers have emerged from tools developed to study quantum gravity. Finally, we discuss issues that arise in the practical Operation of the surface code, the most widely pursued error correction Working of which can be verified by hand. Where possible, fundamental concepts areĭescribed using the simplest examples of detection and correction codes, the Review, we provide an introductory guide to the theory and implementation of Understanding of current and future quantum computing architectures. As such,įamiliarity with quantum coding is an essential prerequisite for the Physical level to gate compilation strategies at the software level. Influence the full quantum computing stack, from the layout of qubits at the Realisation of quantum computing the choice of error correction code will ![]() Download a PDF of the paper titled Quantum Error Correction: An Introductory Guide, by Joschka Roffe Download PDF Abstract: Quantum error correction protocols will play a central role in the
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