Much of the current research on the development of a quantum computer involves work at very low temperatures. The challenge to make them more practical for everyday use is to make them work at room temperature.
The breakthrough here came from the use of some everyday materials, with details published today in Nature Communications.
A typical modern-day computer represents information using a binary number system of discrete bits, represented as either 0 and 1.
A quantum computer uses a sequence of quantum bits, or qubits. They can represent information as 0 or 1 or any of a series of states between 0 and 1, known as quantum superposition of those qubits.
It's this leap that makes quantum computers capable of solving problems much more quickly and powerfully than today's typical computers.
An electron has a charge and a spin – the spin determines if an atom will generate a magnetic field. The spin can also be used as a qubit as it can undergo transitions between the spin-up and spin-down quantum states, represented classically by 0 and 1.
But the electron spin states therefore need to be robust against "decoherence". This is the disordering of the electron spins during quantum superposition which results in the loss of information.
The electron spin lifetimes are affected by lattice vibrations in a material and neighbouring magnetic interactions. Long electron spin lifetimes exceeding 100 nanoseconds are needed for quantum computing.
Cooling a material to low temperatures close to absolute zero, -273C, does increases the spin lifetime. So too does the use of magnetically pure conducting materials.
So quantum devices using atomically heavy materials such as silicon or metals need to be cooled to low temperatures near absolute zero.
Other materials have been used to perform quantum manipulations at room temperature. But these materials need to be isotopically engineered, which requires large facilities like nuclear reactors, and pose limitations around qubit density.
Molecules such as metal-organic cluster compounds have also been used, but they too require low temperatures and isotopic engineering.
There are clear and established trade-offs to be considered regarding the feasibility of applying a qubit material system for quantum computing.
A conducting material of light atomic weight with a long electron spin lifetime exceeding 100 nanoseconds at room temperature would permit practical quantum computing. Such a material would combine the best aspects of current solid-state material qubit schemes.
We have demonstrated that a long conduction electron spin lifetime in metallic-like material made up of carbon nanospheres can be achieved at room temperature.
This material was produced simply by burning naphthalene, the active ingredient in mothballs.To read more, click here.