A research team at the Center for Quantum Technology at the Korea Institute of Science and Technology (KIST) has implemented a quantum computing algorithm to estimate interatomic bond distances and ground state energies.
The new quantum algorithm can perform chemical accuracy using fewer resources than conventional methods.
It has succeeded in performing accurate calculations without the need for additional quantum error mitigation techniques.
Reoccurring quantum errors
Quantum computers have the disadvantage of rapidly increasing errors as the computational space grows at the current level.
To overcome this, the Variational Quantum Eigensolver (VQE) method, which combines the advantages of classical and quantum computers, has emerged.
VQE is a hybrid quantum algorithm that uses a quantum processing unit (QPU) and a classical processing unit (CPU) to perform faster computations.
Global research teams, including IBM and Google, are investigating it in a variety of quantum systems, including superconducting and trapped-ion systems.
However, qubit-based VQE is currently only implemented in up to 2 qubits in photonic systems and 12 qubits in superconducting systems. It is challenged by error issues that make it difficult to scale when more qubits and complex computations are required.
A quantum algorithm with higher dimensions
Instead of qubits, the team utilised a higher-dimensional form of quantum algorithm called a qudit.
A qudit is a quantum unit with multiple states, including 0, 1, and 2, in addition to the 0 and 1 that a traditional qubit can represent, which is advantageous for complex quantum computations.
In this study, a qudit was implemented by the orbital angular momentum state of a single photon, and dimensional expansion was possible by adjusting the phase of a photon through holographic images.
This allowed for high-dimensional calculations without complex quantum gates, reducing errors.
Commercialising the algorithm
While conventional VQEs from IBM, Google, and others require quantum error mitigation techniques for chemical accuracy, the KIST team’s VQE quantum algorithm achieved chemical accuracy without any error mitigation techniques.
This demonstrates how high accuracy can be achieved with fewer resources, and it shows the potential for widespread application in industries where molecular properties are important.
It is also expected to be useful in solving complex problems such as climate modelling.
“By securing qudit-based quantum algorithm technology that can achieve chemical accuracy with fewer resources, we expect it to be used in various practical fields, such as developing new drugs and improving battery performance,” concluded Dr Hyang-Tag Lim from KIST.
