Are ‘colour molecules’ the key to a room-temperature quantum computer? Premium

Quantum computers use qubits in superposition states, with recent research showing room-temperature qubits in metal-organic frameworks.

A classical computer is a collection of information storage units called bits. These physical devices have two states each, denoted 0 and 1. Any computation that a computer  performs is essentially the result of the manipulation of the states of bits.

Similarly, a qubit is a physical system with two quantum states, and it is the fundamental physical component of a quantum computer. A qubit can exist in one of the two states or – unlike classical computers – a superposed state with contributions from both states.

This superposition is a quantum feature that the bits in conventional computers don’t exhibit. Superposed states, also known as coherent superpositions, are important in quantum information-processing protocols. However, superpositions are fragile. The fragility arises out of the interaction between the qubit and other systems. The more the number of interaction channels, the faster the superposition “decoheres” and the qubit ends up in one of the two states.

A collection of qubits is required to make a quantum device. For this, any group of qubits needs to satisfy a few basic requirements.

One: the qubits should be identical. The qubits can’t be guaranteed to be identical since they need to be manufactured, and some ‘imperfections’ will creep in.

Two: it should be relatively easy to integrate several qubits that can be operated controllably. Here, controllability refers to both the manipulation of individual qubits (a.k.a. “addressability”) and qubit-qubit interactions. An important, related aspect is the qubit system should be robust enough to function at room temperature without losing quantum features for reasonably long durations.

Many different physical systems are suitable for realising qubits. Some well-studied and practical options include superconducting junctions, trapped ions, and quantum dots. However, all these systems can operate as qubits only at very low temperatures or in a high vacuum or both.