A quantum MRI machine for biomolecular imaging

Melbourne researchers have developed a way to radically miniaturise a magnetic resonance imaging (MRI) machine using atomic-scale quantum computer technology. The system would be capable of imaging the structure of a single biomolecule and has been described in the journal Nature Communications.

The work was led by Professor Lloyd Hollenberg from the University of Melbourne, who noted, “Determining the structure of biomolecules such as proteins can often be a barrier to the development of novel drugs.” So while current techniques create a crystal of the molecule to be studied and use X-ray diffraction to determine the molecule’s average structure, the crystallisation and averaging processes may lead to important information being lost. Also, not all biomolecules can be crystallised — particularly proteins associated with cell membranes, which are critical in the development of new drugs.

Working with researchers at the ARC Centre of Excellence for Quantum Computation and Communication Technology (CQC2T), Professor Hollenberg proposed the use of atomic-sized quantum bits (qubits), normally associated with quantum computers, as highly sensitive quantum sensors to image the individual atoms in a biomolecule. He said, “By using quantum sensing to image individual atoms in a biomolecule, we hope to overcome several issues in conventional biomolecule imaging.

“Our system is specifically designed to use a quantum bit as a nano-MRI machine to image the structure of a single protein molecule in their native hydrated environments,” added Professor Hollenberg.

So how would it work? The study’s lead author, University of Melbourne PhD researcher Viktor Perunicic, explained, “In a conventional MRI machine, large magnets set up a field gradient in all three directions to create 3D images. In our system, we use the natural magnetic properties of a single atomic qubit.” Atomic qubits can be made to exist in two states at the same time, underpinning their potential sensitivity as nanosensors.

“The system would be fabricated on-chip, and by carefully controlling the quantum state of the qubit probe as it interacts with the atoms in the target molecule, we can extract information about the positions of atoms by periodically measuring the qubit probe and thus create an image of the molecule’s structure,” continued Perunicic.

According to Professor Hollenberg, “The construction of such a quantum MRI machine for single-molecule microscopy could revolutionise how we view biological processes at the molecular level, and could lead to the development of new biotechnology and a range of clinical applications.” He added that such a system could be constructed and tested relatively quickly using diamond-based qubits; alternatively, CQC2T’s silicon-based qubits have the long quantum coherence with which to capture high-resolution molecular images in the longer term.