New Materials Could Make Quantum Computers More Practical
Building Quantum Computers
One possible way to build quantum computers would be to use lasers to isolate spinning electrons inside a semiconductor material. When the laser hits the electron, it shows how the electron is spinning by emitting one or more light particles. The spin states can then be used as the most fundamental building blocks for quantum computing, the same way conventional computing uses 1s and 0s.
According to Stanford electrical engineering Professor Jelena Vuckovic, who has been investigating these new materials to build quantum computers, quantum computing would be ideal for studying biological systems, doing cryptography, or data mining, as well as for any other complex problem that can’t be solved by conventional computers.
“When people talk about finding a needle in a haystack, that’s where quantum computing comes in,” said Vuckovic.
The challenge in isolating spinning electrons is finding a material that can confine the electrons when the lasers hit them. Vuckovic’s team has identified three materials that can potentially do this: quantum dots, diamonds, and silicon carbide.
Quantum Dots
A quantum dot is a small amount of indium arsenide inside a crystal of gallium arsenide. The atomic properties of the two materials are known to trap spinning electrons.
In a recent paper, Kevin Fischer, a graduate student in the Vuckovic lab, described how the laser-electron processes can be used within a quantum dot system to control the input and output of light. For instance, by applying more power behind the lasers, two photons could be emitted instead of one. This could be used as an alternative to the 1s and 0s of conventional computers.
One issue is that the quantum dot system still requires cryogenic cooling, which doesn’t make it a suitable candidate for general-purpose computing.
Diamond Color Centers
Vuckovic’s team has also been investigating modifying the crystalline lattice of a diamond to trap light in what is known as a color center. The team replaced some of the carbon atoms in the diamond’s crystalline lattice with silicon atoms.
Like the quantum dots approach, doing quantum computing within diamond color centers requires cryogenic cooling.
Silicon Carbide
Silicon carbide is a hard and transparent crystal that is used to make clutch plates, brake pads, and bulletproof vests, among other things. Prior research has shown that silicon carbide could be modified to create color centers at room temperature, but not in a way that’s efficient enough to create a quantum chip.
Vuckovic’s team was able to eliminate some of the atoms in the silicon carbide lattice to create much more efficient color centers. The team also fabricated nanowires around the color centers to improve photon extraction.
Trapping electrons at room temperature could be a significant step forward for quantum computers, according to Vuckovich. However, she and her team are also not sure which method to create a practical quantum computer will work best in the end.
Quantum Supremacy
Some of the biggest technology companies in the world are working on building quantum computers right now, including Google, IBM, and Microsoft. Teams at many universities around the world are also experimenting with different approaches to building quantum computers.
Both Google and IBM believe we’ll reach “quantum supremacy”--the point when quantum computers will be faster than conventional computers at solving a certain type of complex problems--when quantum computers have around 50 qubits (from the fewer than 10 qubits they do now). The two companies expect this goal to be reached in the next few years.
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Right. I'll wait. Right now, this tech looks like the scientific equivalent of "Cold Fusion".
Cold fusion, on the other hand, is debunked and not being seriously worked on. There's no real theory that explains how it would work if it did work.
There are countless of promising future technologies that have been proven in labs but never got commercialized because no economically viable way was found to manufacture products based on them or by the time that viable manufacturing became viable, something else came along and rendered them useless.
Nuclear fusion is one example of technology that scientists originally thought would take only 20-30 years to research and 50 years later, a commercially viable implementation is still elusive. For quantum computers, the output is a statistical distribution of possible results and the amount of uncertainty increases with every qubit added, so you have the challenges of packing more qubits together, reducing the amount of output noise, finding suitable room-temperature materials to make them from, finding ways to get data in and out of them, etc
I get a feeling that the more scientists research quantum computing, they'll discover that there is even more that they still don't know about and that commercially viable quantum computing is further away than they thought.
Well, the thing is, what's the alternative? Our current processing technology won't last. Moore's Law gave up the ghost long ago as transistor count got so high and gate size has gotten so small. It's at the point now where it can't get much smaller without needing so much error correction that it's overall performing worse than its predecessors. So, clearly, we need something new. And, well, right now, this is the most promising technology we've stumbled on. So, let's research and develop it and see what it's worth. If it's not worth anything, oh well. Something will have been learned, at the very least. No reason to not, until some other technology appears and proves itself more promising, assuming such a thing happens.
Moore's law still has ~10 more years to go - transistor counts are still going up, spectacularly so if you consider 3D-NAND. Logic chips could go 3D too, but we need far more power-efficient transistors first as it would be effectively impossible to cool a ~1000W stack of 16 modern CPUs with a ~160sqmm HSF contact patch.
With Intel saying they are going to introduce a new architecture after 2020, I'm wondering if we're not going to see Xeon Phi cores in a desktop processor. If so, how many and at what clock?
I could imagine that happening in a sort of big-little mix like what is done on mobile with A72/A53: strong cores (Cannonlake-like) to run software that depends heavily on a few threads' performance and a bunch of simpler cores (Atom/Phi) to run less compute-intensive background tasks and massively threaded software.