New Quantum Computing Research Plots Safe Journey Through the Past

A new paper published in the Nature journal Quantum Information explores the quantum computing potential of time travel. It's a very particular mode of theoretical time travel, one that demands a careful balance of manipulation of quantum entanglement and the right grasp of general relativity.

The idea emerges from the field of quantum computing, in which scientists look to the computational potential of quantum-mechanical phenomena. It's the realm of superposition and entanglement. According to physicist David Deutsch, the superposition of qubits (quantum bits of information that can simultaneously exist as a one and a zero and everything in between) can theoretically allow a quantum computer to work on a million computations at once. Entangling those qubits allows us to measure each one's value without disturbing the system's integrity.


Lest you have doubts about the reality of quantum computers, Google says that it has created one that works 100 million times faster than our laptops. But why dream small? Perhaps, as researcher Dave Bacon posits, you could enable your quantum computer to send particles backward through time along a "closed timelike curve." Think of that curve as a wormhole that loops back around to the same point in space-time.

What's the point of such a voyage? Well, blasting information-coded particles through such a time loop could super-charge a quantum computer enough to solve some otherwise impossible computations.

Yet this is still time travel into the past, so we have to consider the rules of causality. In this universe, cause always comes before effect, not the other way around. There's no killing your own grandfather or assassinating Hitler allowed.

Critics of the closed timelike curve theory of quantum computing argue that causality would break up the theoretical computing party as the time-traveling particle would interact with its past self. But now, in this latest study, a team of international quantum researchers argue that by quantum entangling a time-traveling quantum computation particle, you could "lock it," resulting in an "open timelike curve." You wouldn't have to worry about broken causality because the curve is open, not closed. The locked particle can't interact with its past self.

That's the theory in a nutshell, but you'll want to read "How Quantum Computers Work" and the original quantum information paper for a deeper dive into the topic.