Frontiers of Engineering Reports on Leading-Edge Engineering from the 2002 NAE Symposium on Frontiers of Engineering (2003) / Chapter Skim
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Engineering Challenges for Quantum Information Technology
Engineering Challenges for Quantum Information Technology
Pages 91-108
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From page 93... ...
Every language contains structure particularly certain letters or letter combinations that appear more often than others and, if one is not careful, encrypted texts reveal the same structure. Nowadays we know that the only secure way of encrypting a text is by shifting each letter by a random amount.
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From page 94... ...
Once they have an upper bound, Alice and Bob can distill, by purely classical privacy amplification techniques, a shorter random key that is secure to an arbitrary degree. In a simplified example, let's suppose Alice and Bob share two random bits, but they know an eavesdropper knows at most one.
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From page 95... ...
Future research will focus on two aspects of QKD miniaturization of the devices and improved secure bit rates and longer distances for secure key distribution. The latter will require the development of better single-photon detectors
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From page 96... ...
In addition, until "lossless" fibers are developed, the only technique for overcoming fiber losses is quantum error correction, which is a challenging task, comparable in difficulty to building a small quantum computer (van Enk et al., 1998~. Despite the challenges that lie ahead, quantum mechanics will someday make communications more secure.
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From page 97... ...
For example, because most modern encryption schemes work on the assumption that it is inefficient to find prime factors of large numbers, a quantum computer would put the safety of all of these schemes in jeopardy. Shor's algorithm also raised hopes that other quantum algorithms could outperform their classical counterparts.
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From page 98... ...
Even if the output collapses to only one of the factors upon readout, we can divide our large number by that factor and thus simplify the original problem. ION TRAPS, A SUCCESS STORY In 1989, Wolfgang Paul and Hans Dehmelt won the Nobel Prize for their work on ion traps.
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From page 99... ...
gates on two and four ions (Sackett et al., 2000~. In the same year, David DiVincenco published five criteria for quantum computation that have been widely adopted as a test for determining if a physical system is a serious candidate for quantum computing (DiVincenco, 2001~.
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From page 100... ...
In this trap array, we moved an ion from area 2 to area 4 within 28 ,us, while preserving the qubit information, and we separated two ions trapped in area 3 into areas 2 and 4, thereby proving the feasibility of two main ingredients of the multitrap scheme (Rowe et al., 2002~. We have just verified the final ingredient, cooling of the qubit-ion species with a different species without disturbing the qubit information.
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From page 101... ...
clamped by two alumina wafers. FIGURE 4 Schematic drawing of the prototype silicon trap for one ion (shown as a dot in the center hole)
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From page 102... ...
2000. Quantum Computation and Quantum Information.
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From page 103... ...
have only recently been demonstrated (Nakamura et al., 1999; Vion et al., 2002~. Nevertheless, there is a great deal of optimism that solid-state implementations of quantum computers will ultimately lead to scalable architectures in the same way that the invention of the transistor and integrated circuit presaged the development of large-scale and networked conventional computers.
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From page 104... ...
A major surprise in the early days of quantum computing theory was that quantum error correction was possible at all; it has been shown that if a qubit of quantum information is redundantly coded into several qubits, errors in quantum computation can be reduced just as they can be corrected in classical commun~cations channels (Nielsen and Chuang, 2000~. One certainty is that the operation of scalable quantum computers will rely heavily on error correction.
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From page 105... ...
Efficient on-chip quantum communication will be essentialfor the development of large-scale solid-state quantum computing. Communication between devices is also important in conventional computers, but the need for quantum error correction necessitates the continuous transfer of redundant qubits throughout the computer.
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From page 106... ...
The major difficulty with spin-based implementations of quantum computers is that they require measurement and control of single electron spins or nuclear spins, a task that is only now on the threshold of realization. Scalable spin-based quantum computing will probably require the development of a new technology in which single atoms can be accurately positioned to create devices with the precision necessary for quantum computation.
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From page 107... ...
Voltage pulses applied to metal gates on the top of the structure control the positions of electrons inside the silicon. FIGURE 3 One possible route to the realization of single-spin quantum logical devices in silicon (Si)
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From page 108... ...
2002. Hydrogenic spin quantum computing in silicon: a digital approach.
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