The realm of quantum computing is something that is still generally considered a large unexplored frontier, with the mastery of creating quantum circuits still out of our reach. That is why our knowledge of building quantum computers is hardly at a level where we could compete face-to-face with a modern electronic computer.
But while other researchers around the world are shifting their attention towards making transistors yet again smaller and more efficient, some research groups and tech companies remain undeterred, and still sit at the very forefront of this atomic realm. IBM, one of the largest entities that currently challenges this field of research, has yet again made another achievement that would make the quantum computing revolution closer than ever thought possible.
The Main Challenge in Quantum Computing
Unlike traditional digital circuits where information is always relayed in single values of 1 and 0 “bits”, a quantum computer can relay many values simultaneously for each individual state of an atom, and is called a “qubit”. It is easy to retain one digital bit using simple switches, but a qubit needs the atom to maintain its quantum state to retain its value. If the atom “decoheres”, or falls out of its multi-value state, data is lost, and the information would now be simply treated as a regular digital bit.
What makes this even more challenging is that keeping the multi-value information requires the atoms to be kept at very, very low temperatures, within a superconductive state of an atom. The quantum state itself could also be very delicate, which means that the system could be very, very fragile and difficult to maintain.
IBM’s Superconductor Qubit Chip
The announcement of IBM’s achievement was made last February 28, 2012. The primary construction of IBM’s quantum computer is a set of qubits that is placed on top of a silicon substrate using aluminium and niobium superconductors, where a thin layer of aluminium oxide acts as an insulator between the separate superconductor electrodes. This is the exact system that needs to be kept cooled enough to prevent the atoms from decohering back into a single state.
So far, the longest time that they have achieved in preserving the values of the three-dimensional superconducting qubit was at 100 microseconds (minimum time at 10 microseconds). Quite short, but it’s already a very impressive feat considering that most research institutions could only keep qubit information for a few nanoseconds a decade ago.
The lengthened qubit state preservation time has consequently allowed IBM to build a two-qubit system that functions as a “NOT” logic gate. This means that they could easily change the state of one-qubit by flipping the state of the other, with a success rate of almost 95%.
IBM plans the next step in their quest to break the realm of quantum computers by placing three or five qubits together to create a simple quantum circuit.