Real? Yes
Useful yet? Not so much
How do you write logic for a machine that has 3 states?
(on, off, and maybe...)
Does this mean a .jpeg of my cat can both exist and not exist at the same time?
Technology: Quantum computers
Vancouver startup D-Wave Systems, however, aims to build a quantum computer within three years. It won't be a fully functional quantum computer of the sort long envisioned; but D-Wave is on track to produce a special-purpose, "noisy" piece of quantum hardware that could solve many of the physical-simulation problems that stump today's computers, says David Meyer, a mathematician working on quantum algorithms at the University of California, San Diego.
The difference between D-Wave's system and other quantum computer designs is the particular properties of quantum mechanics that they exploit. Other systems rely on a property called entanglement, which says that any two particles that have interacted in the past, even if now spatially separated, may still influence each other's states. But that interdependence is easily disrupted by the particles' interactions with their environment. In contrast, D-Wave's design takes advantage of the far more robust property of quantum physics known as quantum tunneling, which allows particles to "magically" hop from one location to another.
Incorporated in April 1999, D-Wave originated as a series of conversations among students and lecturers at the University of British Columbia. Over the years, it has amassed intellectual property and narrowed its focus, while attracting almost $18 million in funding, initially from angel investors and more recently from the Canadian and German governments, and from venture capital firms. The company plans to complete a prototype device by the end of 2006; a version capable of solving commercial problems could be ready by 2008, says president and CEO Geordie Rose.
The aggressiveness of D-Wave's timetable is made possible by the simplicity of its device's design: an analog chip made of low-temperature superconductors. The chip must be cooled to -269 °C with liquid helium, but it doesn't require the delicate state-of-the-art lasers, vacuum pumps, and other exotic machinery that other quantum computers need.
The design is also amenable to the lithography techniques used to make standard computer chips, further simplifying fabrication. D-Wave patterns an array of loops of low-temperature superconductors such as aluminum and niobium onto a chip. When electricity flows through them, the loops act like tiny magnets. Two refrigerator magnets will naturally flip so that they stick together, minimizing the energy between them. The loops in D-Wave's chip behave similarly, "flipping" the direction of current flow from clockwise to counterclockwise to minimize the magnetic flux between them. Depending on the problem it's meant to tackle, the chip is programmed so that current flows through each loop in a particular direction. The loops then spontaneously flip until they reach a stable energy state, which represents the solution to the problem. ...
Quantum Calculation - D-Wave Systems is building a 'quantum' computer to solve intractable real-world problems. The secret: cooling the chip to -269 C with liquid helium, MIT's Technology Review, July 2005
What is this? An Advertisement?
It's equally likely that you're not.
Bet it STILL won't run Vista.
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A qubit's most important distinction from a classical bit, however, is not the continuous nature of the state (which can be replicated by any analog quantity), but the fact that multiple qubits can exhibit quantum entanglement. Entanglement is a nonlocal property that allows a set of qubits to express superpositions of different binary strings (01010 and 11111, for example) simultaneously. Such "quantum parallelism" is one of the keys to the potential power of quantum computation. In essence, each independent state of the quantum particle used in the computer can follow its own independent computation path to conclusion while its other states are observed and changed.
A number of qubits taken together is a quantum register. Quantum computers perform calculations by manipulating qubits.
Similarly, a unit of quantum information in a 3-level quantum system is called a qutrit, by analogy with the unit of classical information trit. The term "Qudit" is used to denote a unit of quantum information in a d-level quantum system.
Benjamin Schumacher discovered a way of interpreting quantum states as information. He came up with a way of compressing the information in a state, and storing the information on a smaller number of states. This is now known as Schumacher compression. Schumacher is also credited with inventing the term qubit (See, for example, Phys. Rev. A 51 2738 (1995)).
The state space of a single qubit register can be represented geometrically by the Bloch sphere. This is a two dimentional space which has an underlying geometry of the surface of a sphere. This essentially means that the single qubit register space has two local degrees of freedom. An n-qubit register space has 2n+1 − 2 degrees of freedom. This is much larger than 2n, which is what one would expect classically with no entanglement.
[Wikipedia via Qubit at Quantiki – the free-content WWW resource in quantum information science]