Scientists Have Created a Protein Qubit Inside a Living Cell

Quantum technology is a uniquely poor fit for biology. It requires extreme precision and clean environments free of interference, which couldn’t be further from the environment inside a living cell. Scientists have trouble maintaining the state of a qubit inside enormous, shielded quantum devices, but now researchers from the University of Chicago have created one inside a living mammalian cell.
Actually, they didn’t create it so much as learn how to use it. A paper published in the journal Nature lays out the experiment, in which a long-used protein called enhanced yellow fluorescent protein (EYFP) is proven capable of acting as a qubit.
This is based on an extant feature of EYFP that these researchers discovered, in which certain electrons maintain a so-called “triplet state.” In this state, their collective spins can be manipulated with laser pulses to behave as a qubit, in which their spin states maintain a superposition of states. Scientists can then use light to read this spin state optically.
Subtle pulsing in this spin state, essentially the pattern of disruptions in the qubit’s superposition, can then be read to infer something about the qubit’s surroundings. Referring to this, engineers talk about the information that is “encoded” in the spin state.
Quantum sensors are classically used to detect magnetic fields, electric fields, and temperature, but they can be so accurate in sensing these things that they can investigate the world via tiny variations in those metrics. Quantum sensors, primarily based around electrons trapped in tiny defects engineered into diamonds, have been used to discern neural activity, for instance, or to map mineral deposits underground.
Now, they can be used to discern structures—and perhaps even activity—inside of living mammal cells. This study demonstrates the desired activity not just in distillates, but in living systems as well.
If this technique can be applied as widely as researchers think, the implications will be enormous. Not only could in-vivo precision quantum-scale sensing be used to discern the dynamics of protein folding, but it could also help reveal the processes behind gene expression, certain diseases, and more.
The researchers believe their approach could allow multiple different proteins to be used in this way, which would open the door for multiple simultaneous quantum probes in a single biological process. This could make the impact on biology even more extreme.
Fluorescent proteins have already revolutionized cell biology by allowing direct, topical imaging of cells at the molecular scale. This breakthrough, however, offers the ability to read out certain attributes of living processes at the quantum scale with precision previously unheard of in a biological context.
Also exciting is that the protein motifs necessary to create this triplet state could be engineered into other proteins, or potentially affixed to non-biological substrates. In other words, it doesn’t just open up possibilities for sensing in biology, but for expanded use of quantum sensing in general.
After all, if these optically accessible triplet-state qubits can help live cells, they can be useful just about anywhere.
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