Materials issues for quantum computation
- PDF / 601,013 Bytes
- 7 Pages / 585 x 783 pts Page_size
- 64 Downloads / 186 Views
Introduction In 1982, Richard Feynman wondered about the remarkable ability of quantum systems to compute their own time evolution.1 Could one harness the ability of quantum materials to solve the Schrödinger equation and create a fundamentally new class of computers? Pioneering quantum computer scientists Peter Shor, Lov Grover, and others brought into focus the question of what a quantum computer can achieve that is new and different from ordinary (“classical”) computers. Shor’s algorithm2 provides an exponential speedup in the factoring of large integers, a capability that can efficiently defeat the Rivest–Shamir–Adleman (RSA) public key encryption scheme3 that is widely used on the Internet. Grover demonstrated4 how a quantum database could enable quadratic speedup in search queries. Lloyd proved the correctness of Feynman’s original conjecture5 regarding quantum simulation, setting the stage for efficient quantum simulation of materials. In a quantum computer, information is stored in quantum bits or “qubits,” which can be thought of as a pair of quantum states that are part of “artificial atoms” made by the quantum mechanic. There are various ways of making these artificial atoms, and several of them are described in this issue of MRS Bulletin. They range from ions, which are atomic systems, to
devices made from billions of atoms such as quantum dots and Josephson junctions, which under the right circumstances behave like atomic systems. The internal states of these objects are described quantum mechanically, and for an N-qubit system, the information is contained in the N-body wave function. In most designs, the qubit is formed from only two quantum states out of the many states of the artificial atom that exist, so a qubit is a quantum two-level system. More specifically, the information processed in a quantum computer is contained in the quantum-mechanical amplitudes of each of the N-body, two-level system basis states. These are 2N complex numbers. Such a system of N qubits forms the memory of the quantum computer, and this memory is transformed by physical interactions that must be precisely controlled. To process this information, qubits are made to interact with each other via a pattern of classical control signals (e.g., electromagnetic fields) that couple the qubits and execute quantum logic operations. Such a quantum algorithm results in the evolution of all quantum information. The fact that controlling the interactions between N qubits drives the evolution of 2N complex coefficients is central to why quantum computing is so powerful, at least at some tasks. However, the information stored in these qubits is delicate. The complex amplitudes that specify a qubit can be corrupted
James N. Eckstein, Department of Physics, University of Illinois; [email protected] Jeremy Levy, Department of Physics and Astronomy, University of Pittsburgh; [email protected] DOI: 10.1557/mrs.2013.210
© 2013 Materials Research Society
MRS BULLETIN • VOLUME 38 • OCTOBER 2013 • www.mrs.org/bulletin
783
MATERIALS ISSUES FOR
Data Loading...
