## Seminal Contributions to the Theoretical Foundation of Quantum Information Processing - overview

**Physics Accomplishment | 1993 - 2015**

**IBM researchers: **Charles Bennett, David DiVincenzo, John Smolin, Barbara Terhal, Sergey Bravyi, Nabil Amer

** Where the work was done: **IBM T.J. Watson Research Center

**What we accomplished**: IBM has more than two decades of foundational work in quantum information processing.

IBM's early contributions include quantum teleportation (1993), quantum error correcting codes, mixed state entanglement, and entanglement distillation (1996), uncompletable product bases and bound entanglement (1998), remote state preparation (2000), and the DiVincenzo criteria (2000).

Later contributions start with "Quantum locking," which shows a unique information-theoretic property of quantum transmissions: sending one classical bit can make a vast supply of information accessible by measurement of a quantum state.

Other related discoveries include new methods for classifying and identifying nonlinear quantum codes, new capacity formulas for multi-user and multiply-assisted quantum channels, and new strategies for assessing the secuity of quantum crypto transmissions through noisy channels.

IBM has also done new pioneering work in quantum complexity: It has found a new classification of quantum Hamiltonians, which they have called "stoquastic", which faithfully formalizes the idea of the "sign problem" as the key difficulty in quantum simulation. New complexity classes analogous to NP have been constructed now and studied, based on this stoquastic categorization. A general theory of noise has been developed for such systems, and it permits a realistic assessment of the ability to do quantum computation. It has also been applied to a realistic mode of the Koch qubit. The device level analysis of the Koch qubit has been developed over many years of close cooperation between theory and experiment.

**Related links**: Quantum teleportation

Image credit: Physikalisches Institut. Quantum computer and the DiVincenzo criteria

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