One-way quantum computer

The one-way or measurement based quantum computer is a method of quantum computing that first prepares an entangled resource state, usually a cluster state or graph state, then performs single qubit measurements on it. It is "one-way" because the resource state is destroyed by the measurements.

The outcome of each individual measurement is random, but they are related in such a way that the computation always succeeds. In general the choices of basis for later measurements need to depend on the results of earlier measurements, and hence the measurements cannot all be performed at the same time.

Equivalence to quantum circuit model

Any one-way computation can be made into a quantum circuit by using quantum gates to prepare the resource state. For cluster and graph resource states, this requires only one two-qubit gate per bond, so is efficient.

Conversely, any quantum circuit can be simulated by a one-way computer using a two-dimensional cluster state as the resource state, by laying out the circuit diagram on the cluster; Z measurements (\{|0\rangle,|1\rangle\} basis) remove physical qubits from the cluster, while measurements in the X-Y plane (|0\rangle\pm e^{i\theta}|1\rangle basis) teleport the logical qubits along the "wires" and perform the required quantum gates.[1] This is also polynomially efficient, as the required size of cluster scales as the size of the circuit (qubits x timesteps), while the number of measurement timesteps scales as the number of circuit timesteps.


One-way quantum computation has been demonstrated by running the 2 qubit Grover's algorithm on a 2x2 cluster state of photons.[2][3] A linear optics quantum computer based on one-way computation has been proposed.[4]

Cluster states have also been created in optical lattices,[5] but were not used for computation as the atom qubits were too close together to measure individually.


  1. ^ R. Raussendorf, D. E. Browne, and H. J. Briegel (2003). "Measurement based Quantum Computation on Cluster States". Phys. Rev. A 68 (2): 022312. arXiv:quant-ph/0301052. doi:10.1103/PhysRevA.68.022312. 
  2. ^ P. Walther, K. J. Resch, T. Rudolph, E. Schenck, H. Weinfurter, V. Vedral, M. Aspelmeyer and A. Zeilinger (2005). "Experimental one-way quantum computing". Nature 434 (7030): 169. doi:10.1038/nature03347. PMID 15758991. 
  3. ^ Robert Prevedel, Philip Walther, Felix Tiefenbacher, Pascal Böhi, Rainer Kaltenbaek, Thomas Jennewein and Anton Zeilinger (2007). "High-speed linear optics quantum computing using active feed-forward". Nature 445 (7123): 65–69. doi:10.1038/nature05346. PMID 17203057. 
  4. ^ Daniel E. Browne, Terry Rudolph (2005). "Resource-efficient linear optical quantum computation". Physical Review Letters 95 (1): 010501. arXiv:quant-ph/0405157. Bibcode 2005PhRvL..95a0501B. doi:10.1103/PhysRevLett.95.010501. PMID 16090595. 
  5. ^ Olaf Mandel, Markus Greiner, Artur Widera, Tim Rom, Theodor W. Hänsch and Immanuel Bloch (2003). "Controlled collisions for multi-particle entanglement of optically trapped atoms". Nature 425 (6961): 937. doi:10.1038/nature02008. PMID 14586463. 

Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Quantum computer — A quantum computer is a device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (or conventional) computer, information is… …   Wikipedia

  • Trapped ion quantum computer — A Trapped ion quantum computer is a type of quantum computer. Ions, or charged atomic particles, can be confined and suspended in free space using electromagnetic fields. Qubits are stored in stable electronic states of each ion, and quantum… …   Wikipedia

  • Nuclear magnetic resonance quantum computer — Molecule of alanine used in NMR implementation of quantum computing. Qubits are implemented by spin states of the black carbon atoms NMR quantum computing uses the spin states of molecules as qubits. NMR differs from other implementation …   Wikipedia

  • One-Shot Entanglement-Enhanced Classical Communication — In the theory of quantum communication, it is well known that entanglement cannot increase the capacity of a classical communication channel in the sense of Shannon, that is, for an i.i.d. (independent and identically distributed) protocol.… …   Wikipedia

  • Quantum finite automata — In quantum computing, quantum finite automata or QFA are a quantum analog of probabilistic automata. They are related to quantum computers in a similar fashion as finite automata are related to Turing machines. Several types of automata may be… …   Wikipedia

  • Quantum channel — In quantum information theory, a quantum channel is a communication channel which can transmit quantum information, as well as classical information. An example of quantum information is the state of a qubit. An example of classical information… …   Wikipedia

  • Quantum information — For the journal with this title, see Historical Social Research. In quantum mechanics, quantum information is physical information that is held in the state of a quantum system. The most popular unit of quantum information is the qubit, a two… …   Wikipedia

  • Quantum digital signature — A Quantum Digital Signature (QDS) refers to the quantum mechanical equivalent of either a classical digital signature or, more generally, a handwritten signature on a paper document. Like a handwritten signature, a digital signature is used to… …   Wikipedia

  • Quantum mind — theories are based on the premise that quantum mechanics is necessary to fully understand the mind and brain, particularly concerning an explanation of consciousness. This approach is considered a minority opinion in science, although it does… …   Wikipedia

  • Quantum error correction — is used in quantum computing to protect quantum information from errors due to decoherence and other quantum noise. Quantum error correction is essential if one is to achieve fault tolerant quantum computation that can deal not only with noise on …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.