D-Wave Two

D-Wave Two (project code name Vesuvius) is the second commercially available quantum computer, and the successor to the first commercially available quantum computer, D-Wave One. Both computers were developed by Canadian company D-Wave Systems.^[1] The computers are not general purpose, but rather are designed for quantum annealing. Specifically, the computers are designed to use quantum annealing to solve a single type of problem known as quadratic unconstrained binary optimization.^[2] As of 2015, it is still heavily debated whether large scale entanglement takes place in D-Wave Two, and whether current or future generations of D-Wave computers will have any advantage over classical computers.^{[3][4][5][6][7][8][9]}

D-Wave Two boasts an approximately 512-qubit CPU, an increase over the approximately 128 qubit chips of the D-Wave One series^[10] Available qubit numbers can vary significantly from chip to chip due to flaws in the manufacturing process.^[11] The increase in qubit count for the D-Wave Two was accomplished by tiling qubit pattern of the D-Wave One. This pattern, named chimera by D-Wave Systems, has a limited connectivity such that a given qubit can only interact with at most six other qubits.^[9] As with the D-Wave One, this restricted connectivity greatly limits the optimization problems that can be approached with the hardware.^[11]

In March 2013, several groups of researchers at the Adiabatic Quantum Computing workshop at the Institute of Physics in London produced evidence of quantum entanglement in D-Wave CPUs.^[12] Additionally, in March 2014, researchers from University College London and University of Southern California supported that, finding that the D-Wave Two showed the quantum physics outcome that it should while not showing three different classical physics outcomes.^[13][14]

In May 2013, Catherine McGeoch verified that D-Wave Two finds the solution to the problems it is supposed to solve by comparing the machine against a general purpose solver (CPLEX) which proves optimality. Her work was concerned with demonstrating the correctness of the device, but is often being incorrectly cited by public media as a head-to-head benchmark. It has repeatedly been shown that D-Wave Two is no faster than an ordinary laptop.^[15][16] In April 2013, an arXiv paper by Boixo demonstrated that simulated annealing only needs about a second on a laptop to solve the type of problems considered by McGeoch.^[15] The paper appeared in Nature Physics in February 2014.^[17] Independently, Alex Selby demonstrated that a well-designed heuristic algorithm was about as fast as D-Wave Two in June 2013. In addition Jean Francois Puget from IBM demonstrated that, if tuned correctly, CPLEX is about 10-15 times faster than D-Wave^[18] which ultimately demonstrates that the claims about 3,600 times speedup or more is completely incorrect.

A D-Wave Two in the Quantum Artificial Intelligence Lab at the NASA Advanced Supercomputing Division of Ames Research Center is used for research into machine learning and related fields of study. NASA, Google, and the Universities Space Research Association (USRA) started the lab in 2013.^{[19][20][21][22]}

References

External links

• Google tests D-Wave 2
• Quantum computing is here! But does it run Linux?