Space & Innovation

Quantum Computer to Log Onto Quantum Internet

In recent months, scientists have made important strides toward the amazing and quirky world of quantum computing.

When it comes to data crunching, quantum computers will leave today's fastest processors in the dust.

For starters, a quantum computer would be able to store more bits of information in its memory than there are particles in the universe. And where a conventional silicon-based computer handles one computation at a time in sequence, a quantum computer would work on millions at once.

That kind of staggering power would give a single quantum computer the ability to simulate a whole world in a holographic environment, replicate biological systems to understand diseases and find cures, solve the loads of equations necessary to create extremely accurate weather forecasting and simulate how subatomic particles interact, showing fundamentally how everything in the universe works.

Several quantum computers linked together would make a quantum Internet so powerful that search engines would respond to queries almost like a human being, answering questions immediately and in any language.

In recent months, different groups of scientists and engineers have made important strides toward this amazing new world. They have built machines that can store quantum particles, control them, observe them and send them over fiber-optic cables.

For people in the field, it's an exciting time. "We're gradually removing the stumbling blocks," said Bill Munro, a research scientist at Japanese phone giant NTT, who has done extensive research into quantum computing. "We've shown with the initial experiments that (quantum computing) can work."

Some of the most recent work published in this area has come from scientists at Aalto University in Finland, who have found a way to store quantum particles, see them and change them.

Like conventional computers, quantum computers work by manipulating bits of information. In current computers and laptops, the bits are comprised of electrons, the magnetic fields of metal particles on a disk or the open and closed circuits on a microchip. They're stored as "0s" or "1s" and long strings make the binary code that's the essence of every program.

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In quantum computers, the bits are actually not physical particles, but units of information called qubits that describe the state of particles, including atoms and subatomic particles, such as ions, electrons and photons. For example, a qubit might be represented by the direction in which an electron spins or the polarization of a photon of light – that is, how it's oriented.

Qubits can be either a "0" or a "1," or both a "0" and a "1" simultaneously -- a characteristic called superposition, which is what gives a quantum computer its extraordinary ability to process so much information at once. And like regular electronic bits, qubits need to be controlled and stored in order to get a desired input or output. You need some way to interface with them, just like you need a mouse or a keyboard to interface with the bits in a PC.

But there's a major catch: qubits are easily disturbed by photons of light or heat or just about anything else in the natural environment. As soon as one tries to interact with a qubit, its value changes and it can even lose its crucial superposition characteristic.

In February, Mika Sillanpää and his colleagues at Aalto University reported that they had found a way to interact with a qubit without messing with its superposition.

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They built a tiny device that simulates the quantum state of a single atom. Sillanpää calls his device a kind of "artificial atom" (above). It consisted of a tiny piece of aluminum attached to a bit of sapphire. The scientists connected this component to a small piece of material capable of vibrating, called a resonator.

They put both components into a small cavity and cooled them to just above absolute zero. That turned the aluminum into a superconductor. Superconductors are known for conducting electricity with no resistance and can also behave as single atoms, entering a quantum state.

When the aluminum entered a quantum state, its energy made the resonator vibrate in a particular way. The vibration stored the quantum state information, or qubit. At the same time, it transferred energy into the cavity, which emitted a microwave photon that could be detected. It was the first time anyone had turned a bit of quantum information into a mechanical motion linking qubits to the outside world. It's like an electron inside a conventional computer being converted into a pixel of text on a screen.

Silanpää told Discovery News that theoretically, by reversing the steps and firing a microwave photon at the component, the scientists would be able to change the quantum state of the artificial atom. A successful experiment demonstrating this -- next on his list -- would be similar to having a keyboard that entered new information into a computer.

This kind of link, or interface, between the quirky energy states of quantum particles and the macro world of tangible computers is necessary if we're ever going to harness quantum power.

NTT scientist Bill Munro said since the device allowed for reading and writing qubits, it was a big step toward a useful computing device.

Meanwhile, at Yale, in January, a team of physicists found a way to observe qubits without ruining their superposition. Instead of interacting with the qubits directly, the team took partial measurements of the particle's quantum state. They still disturbed the qubit, but it was in a known way, so they could correct for it.

This research goes some way to building quantum computers. But alone, these machines wouldn't make an Internet; they need to be connected and exchange information. That's where sending qubits over long distances comes into play.

At the University of Innsbruck, Andreas Stute and his colleagues did this with ionized atoms. The researchers put a single calcium ion between two highly reflective mirrors. They hit the ion with a laser, which changed its quantum state, writing a single qubit of information onto it. They then hit the ion with a second laser. The ion emitted a photon, which carried the qubit they wrote down a fiber optic cable.

Last year, a similar experiment, with un-ionized atoms of rubidium, was conducted at the Max Planck Institute of Quantum Optics in Germany. Stephan Ritter, a physicist there, led a group that transmitted the rubidium atom's quantum state from one "node" of a network to another.

Both sets of experiments are important to building a quantum Internet, as they demonstrate that qubits can travel long distances.

Making a quantum computer and full-on Internet is still hard -- and still some years away. But even with the challenges, it's clear that quantum computers that outperform the familiar electronic ones are coming. It's just a question of when.

"Many, though not all, of the fundamental questions about whether such computer are possible in principle have been answered," Munro said. "Now we can get to real R&D."