Scientists have built a qubit, or quantum bit, that can achieve “quantum coherence” at room temperature, something that is normally only possible at temperatures close to Absolute zero.
To achieve quantum coherence, a stable state in which the strange laws of quantum mechanics It can be seen that qubits typically must be cooled to minus 459 degrees Fahrenheit (minus 273 degrees Celsius) or they succumb to perturbations and fail, known as decoherence.
To solve this, the new qubit used a pentacene-based chromophore, a dye molecule that absorbs light and emits color, embedded in a new metal-organic framework (MOF). Its properties allowed scientists to briefly observe quantum coherence at room temperature, the scientists said in a new paper published Jan. 3 in the journal Scientific advances.
While classical computers encode data in bits (expressed as 1 or 0), quantum computers use qubits, which can be expressed as a superposition of 1 and 0, meaning they can be in both states at the same time until are physically observed.
Most physical qubits create a superposition between the spin-up and spin-down positions of an electron: two binary states that behave like 1 and 0. Typically they are a metal line, or a small loop, that behaves like an atom. Google uses aluminum in its qubits, while IBM uses a mixture of aluminum and niobium, according to American scientist.
Multiple qubits can also be joined together, encoding information through electron spin. quantum entanglement (when the states of two or more particles are linked), meaning that entangled qubits can exist in many states simultaneously. This is what makes quantum computers potentially much more powerful than classical ones if they are built with enough qubits.
How the new type of qubit works
Electrons in chromophores can be excited by a process called singlet fission, in which they absorb light and change their spin states. In the past, researchers used singlet fission to create superposition in qubits, but they only achieved this below -324 F (-198 C), the scientists wrote in the paper.
For the new study, the scientists used a chromophore based on the hydrocarbon pentacene, in which pentagonal rings of carbon and hydrogen are linked. To achieve this same quantum state at higher temperatures, the researchers trapped the chromophore molecules in the MOF, a single crystalline material composed of metal ions and held together by organic molecules.
The MOF almost completely restricted the movement of the dye molecule, helping to keep the excited electrons in an entangled state. The scientists then excited the chromophore’s electrons through singlet fission by exposing them to microwave pulses. Small holes in the crystal structure, known as nanopores, allowed electrons to rotate at a small, specific angle, according to the study’s lead author. Nobuhiro Yanaiassociate professor of chemistry at Kyushu University, said in a statement.
This slight rotation allowed the excited electrons to go from two pairs of electrons in excited “triplet states” (in which electrons from different molecular orbits have parallel spins) to a set of four electrons in the less stable “quintet state”, in The electron spins are antiparallel, meaning they are parallel but move in opposite directions. In this quintet state the laws of quantum mechanics dominate.
After this process, the researchers observed quantum coherence in these four electrons in the quintet state for more than 100 nanoseconds at room temperature (a nanosecond is one billionth of a second).
Searching for quantum computers at room temperature
It is the first room-temperature quantum coherence of entangled quintet-state electrons, the study’s co-author said. Yasuhiro Koboriprofessor of chemistry at Kobe University, in the statement.
In follow-up work, the team hopes to create more stable qubits by adding other “guest” molecules that further restrict the movement of electrons, or by tinkering with the underlying structure of the MOF, Yanai said in the statement.
While the new research is unlikely to lead to room-temperature quantum computing in the foreseeable future, the advance adds to work that has been done to build qubits that can achieve quantum coherence at room temperature. In fact, producing stable qubits at room temperature has long been a hope, Vlatko Vedrala professor of quantum information science at the University of Oxford told Live Science.
This calculation at room temperature would avoid the need to correct errors, he said. This is because to operate at room temperature, qubits, by design, would have to resist disruptive forces that make them unstable and prone to decoherence.
“In this paper, long spin coherence times are reported, which is a significant advance,” he said. “However, I am not sure how easy it is to scale this up, and in particular how easy it is to control interactions between qubits. It seems to me that this will be the bottleneck, since isolated qubits with long coherence times will not “They are very useful for quantum computing.” In other words, to make a powerful computer, many qubits are needed to perform calculations.
Despite questioning the usefulness of this specific discovery, Vedral hailed it as “an important milestone,” adding that this body of research is more promising in the long term than developing ways to perform quantum error correction.