Computational model underlying the one-way quantum computer

2002 ◽  
Vol 2 (6) ◽  
pp. 443-486
Author(s):  
R. Raussendorf ◽  
H. Briegel
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Computational Model ◽  
Quantum Logic ◽  
Quantum Information Processing ◽  
Quantum Computer ◽  
Quantum Circuit ◽  
Single Step ◽  
Clifford Group ◽  
The One

In this paper we present the computational model underlying the one-way quantum computer which we introduced recently [Phys. Rev. Lett. {\bf{86}}, 5188 (2001)]. The one-way quantum computer has the property that any quantum logic network can be simulated on it. Conversely, not all ways of quantum information processing that are possible with the one-way quantum computer can be understood properly in network model terms. We show that the logical depth is, for certain algorithms, lower than has so far been known for networks. For example, every quantum circuit in the Clifford group can be performed on the one-way quantum computer in a single step.

scholarly journals Quantum Mechanics and the Origin of Life

2004 ◽  
Vol 213 ◽  
pp. 237-244
Author(s):  
Paul Davies
Keyword(s):  
Quantum Mechanics ◽  
Information Processing ◽  
Quantum Information ◽  
Quantum Computation ◽  
Origin Of Life ◽  
Quantum Information Processing ◽  
Quantum Computer ◽  
The Origin Of Life ◽  
Concept Of Information

The race to build a quantum computer has led to a radical re-evaluation of the concept of information. In this paper I conjecture that life, defined as an information processing and replicating system, may be exploiting the considerable efficiency advantages offered by quantum computation, and that quantum information processing may dramatically shorten the odds for life originating from a random chemical soup. The plausibility of this conjecture rests, however, on life somehow circumventing the decoherence effects of the environment. I offer some speculations on ways in which this might happen.

EXPLORING A NEW POST-SELECTION CONDITION FOR EFFICIENT LINEAR OPTICS COMPUTATION

2005 ◽  
Vol 03 (04) ◽  
pp. 611-621
Author(s):  
RUBEN COEN CAGLI ◽  
PAOLO ANIELLO ◽  
NICOLA CESARIO ◽  
FRANCESCO FONCELLINO
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Upper Bound ◽  
Quantum Information Processing ◽  
Single Photon ◽  
Success Probability ◽  
Rigorous Proof ◽  
Linear Optics ◽  
Selection Condition ◽  
The One

Recently, it has been shown that fundamental gates for theoretically efficient quantum information processing can be realized by using single photon sources, linear optics and photon counters. One of these fundamental gates is the NS-gate, that is, the one-mode non-linear sign shift. In this work, firstly, we prove by an elementary and rigorous proof that the upper bound of success probability of NS-gates with only one helper photon and an undefined number of ancillary modes is bounded by 0.25. Secondly, we explore the upper bound of the success probability of the NS-gate with a new post-selection measurement. The idea behind this new post-selection measurement is to condition the success of NS-gate transformation to the observation of only one helper photon in whichever of the output modes.

Quantum information processing

2009 ◽  
Author(s):  
Stephen Barnett
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Unitary Transformation ◽  
Quantum Information Processing ◽  
Quantum Computer ◽  
Quantum Evolution ◽  
Quantum Computers ◽  
Digital Electronics ◽  
Logic Operations ◽  
And Control

We have seen how information can be encoded onto a quantum system by selecting the state in which it is prepared. Retrieving the information is achieved by performing a measurement, and the optimal measurement in any given situation is usually a generalized measurement. In between preparation and measurement, the information resides in the quantum state of the system, which evolves in a manner determined by the Hamiltonian. The associated unitary transformation may usefully be viewed as quantum information processing; if we can engineer an appropriate Hamiltonian then we can use the quantum evolution to assist in performing computational tasks. Our objective in quantum information processing is to implement a desired unitary transformation. Typically this will mean coupling together a number, perhaps a large number, of qubits and thereby generating highly entangled states. It is fortunate, although by no means obvious, that we can realize any desired multiqubit unitary transformation as a product of a small selection of simple transformations and, moreover, that each of these need only act on a single qubit or on a pair of qubits. The situation is reminiscent of digital electronics, in which logic operations are decomposed into actions on a small number of bits. If we can realize and control a very large number of such operations in a single device then we have a computer. Similar control of a large number of qubits will constitute a quantum computer. It is the revolutionary potential of quantum computers, more than any other single factor, that has fuelled the recent explosion of interest in our subject. We shall examine the remarkable properties of quantum computers in the next chapter. In digital electronics, we represent bit values by voltages: the logical value 1 is a high voltage (typically +5 V) and 0 is the ground voltage (0 V). The voltage bits are coupled and manipulated by transistor-based devices, or gates. The simplest gates act on only one bit or combine two bits to generate a single new bit, the value of which is determined by the two input bits. For a single bit, with value 0 or 1, the only possible operations are the identity (which does not require a gate) and the bit flip.

Integrated optical approach to trapped ion quantum computation

2009 ◽  
Vol 9 (3&4) ◽  
pp. 181-202
Author(s):  
J. Kim ◽  
C. Kim
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Information Processing ◽  
Quantum Computer ◽  
Fault Tolerant ◽  
Trapped Ions ◽  
Physical Realization ◽  
Trapped Ion ◽  
Integrated Optical ◽  
The Physical Realization

Recent experimental progress in quantum information processing with trapped ions have demonstrated most of the fundamental elements required to realize a scalable quantum computer. The next set of challenges lie in realization of a large number of qubits and the means to prepare, manipulate and measure them, leading to error-protected qubits and fault tolerant architectures. The integration of qubits necessarily require integrated optical approach as most of these operations involve interaction with photons. In this paper, we discuss integrated optics technologies and concrete optical designs needed for the physical realization of scalable quantum computer.

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