Some would say we already have quantum computers. It might be more accurate to say we are beginning to have a quantum computing processor. The difference between regularly functional quantum computers and what we have today isn’t just a matter of quaint hardware though right now quantum computing is performed with custom contraptions that can barely operate on one or two qubits (the qubit is the quantum computational analog to the digital computer’s bit). The heart of the difference is a question: What sorts of problems can a quantum computer solve? (Corollary: What problems can a quantum computer solve that a digital computer can’t solve, or can’t solve well.)

While some dream of turning quantum computers onto problems already solvable by today’s digital computers – only solving them much faster; the most tantalizing dreams are of finding problems only a quantum computer can solve. Are there favorite candidates? Sure, solving quantum problems.

Before anyone slaps their forehead and exclaims “Doh!” formulating the right quantum problems for quantum computing is not trivial, especially to work with the technical limitations quantum computing is likely to have for some time. Most think the problems will come from simulating or modeling physical chemistry.

How about calculating the exact amount of energy in molecular hydrogen? A huge team of supercomputers might do it, if anyone could afford it, or lived that long. It’s not that the amount of energy is so large, or small; it’s the precision. For this type of problem, scientists and their traditional computers usually calculate approximations – sometimes using educated guesses at the precision. In other words, the calculations are not all that reliably precise. Quantum processing can grind to very precise calculations in this kind of problem, because measuring the activity (energy) of hydrogen atoms is a matter of quantum physics.

It was the insight – use a quantum processor to solve quantum problems – that led a team of researchers at Harvard University (USA), Oxford University (UK), and the University of Queensland (Australia) to construct a quantum system that calculated the amount of energy in molecular hydrogen. Jacob Biamonte from Oxford University’s Computing Laboratory, and one of the authors of the research put it this way:

The thought process of humans has evolved to reason in the world we live in. Although these effects are crucial to life itself, quantum effects are essentially unnoticeable in our day-to-day lives. Like the conscious thought process of our brain, machines that operate using ‘classical sequences’ face grave difficultly modeling systems, such as molecules, that operate by ‘quantum sequences’.

Quantum sequences are not only difficult for our classical brains to understand, but at least very difficult and likely even impossible to accurately model using any device that operates by classical sequences. Quantum simulators overcome this problem as they naturally operate using quantum sequences – it is just up to our classical brains to ask them the right questions, and many of the most important ones are about quantum chemistry.

[Source: Oxford University]

As a matter of technology, this quantum processing research is one step on a long chain of steps leading to a true quantum computer. What makes scientist’s eyes light up, is that glimmer that comes from the first little opening in the door to a whole world of computing that they’ve never seen before. The ability to run simulations on quantum-level chemical processes, particularly the intricate molecular activity of the organic chemistry that makes up the living world – that is a prospect almost without limit.

Physicists at the National Institute of Standards and Technology (NIST) have demonstrated the first “universal” programmable quantum information processor able to run any program allowed by quantum mechanics—the rules governing the submicroscopic world—using two quantum bits (qubits) of information. The processor could be a module in a future quantum computer, which theoretically could solve some important problems that are intractable today.

The NIST team also analyzed the quantum processor with the methods used in traditional computer science and electronics by creating a diagram of the processing circuit and mathematically determining the 15 different starting values and sequences of processing operations needed to run a given program. “This is the first time anyone has demonstrated a programmable quantum processor for more than one qubit,” says NIST postdoctoral researcher David Hanneke, first author of the paper. “It’s a step toward the big goal of doing calculations with lots and lots of qubits. The idea is you’d have lots of these processors, and you’d link them together.”

The NIST processor stores binary information (1s and 0s) in two beryllium ions (electrically charged atoms), which are held in an electromagnetic trap and manipulated with ultraviolet lasers. Two magnesium ions in the trap help cool the beryllium ions.

NIST scientists can manipulate the states of each beryllium qubit, including placing the ions in a “superposition” of both 1 and 0 values at the same time, a significant potential advantage of information processing in the quantum world. Scientists also can “entangle” the two qubits, a quantum phenomenon that links the pair’s properties even when the ions are physically separated.

With these capabilities, the NIST team performed 160 different processing routines on the two qubits. Although there are an infinite number of possible two-qubit programs, this set of 160 is large and diverse enough to fairly represent them, Hanneke says, making the processor “universal.” Key to the experimental design was use of a random number generator to select the particular routines that would be executed, so all possible programs had an equal chance of selection. This approach was chosen to avoid bias in testing the processor, in the event that some programs ran better or produced more accurate outputs than others.

[Source: EurekAlert]