Quantum Computing Challenges: Protecting Fragile Qubits

Published by whurley (10/10/2017)

Harnessing the Laws of Quantum Mechanics to Build a Quantum Computer

If physicists can work out how to reliably harness certain quantum mechanical phenomena to build a quantum computer, that technology would revolutionize computing. Sounds great, right? But what will a quantum computer be like?

I’ve already shared with you that quantum computers use qubits instead of traditional bits. This key difference allows quantum computers to store and process far more information. That means they could be used for very complex applications that are unreachable with our current machines. I shared the characteristics of qubits in my last post.

Right now scientists are experimenting with many methods of making physical qubits. One option is to use photons, which are particles of light. The polarization of the photon would determine whether it was in a zero state, a one state, or some superposition of the two. Other options are to use the spin of electrons or the spin of the nuclei of atoms.  These are just a few.  In each physical form, qubits are really fragile. They are easily impacted by noise, waves, other particles, and anything else, really. Keeping qubits isolated and in superposition is the first challenge on the road to a robust quantum computer.

Protect. This. Quantum Gate Array.

Scientists currently safeguard fragile qubits by isolating the quantum processor and keeping it at very, very, very low temperatures. Like close to absolute zero low temperatures.  Which means the answer to the question, “What will a quantum computer be like?” is “A big, powerful refrigerator.”  At least in the near term.  Remember, we’re still in the ENIAC stage here.  The scientific term for the problem is “quantum decoherence.”  That means a quantum system that is not isolated loses its quantum behavior (superposition, entanglement) over time.  By keeping the processor isolated and super-cooled, researchers are able to prolong the period of coherence.

Other Challenges to Overcome

In addition to protecting the qubits, error detection and correction and scalability are real obstacles that have to be addressed.  Qubits are more prone to error than classical bits, so finding and fixing those errors will be vital to success. Right now that means adding more qubits, which means the system has to be scalable.  IBM’s current quantum processor only has 17 qubits.

Still, there are hundreds of thousands of dollars out there working hard in research labs to figure these problems out.  Google is currently testing a 20-qubit processor with a low error rate.  The company says its on schedule to produce a 49-qubit chip by the end of the year. This year!  If they are able to do so, that would be a huge step toward building a quantum computer more powerful than our current technology. And that will be a great day.