'Butterfly effect' is wrong and reality can 'heal itself', quantum scientists find in time travel experiment

Sending a qubit through a simulation of the past had it return to the present generally unchanged

PA (PA)

Scientists have disproved the “butterfly effect” at the quantum level, refuting the idea that changes made in the past would have grave ramifications upon returning to the present.

In the simulation, a piece of information is simulated to be sent backwards in time. That information is then damaged. However, when the information returns to the “present” it is largely unaltered and, counter-intuitively, with travels further into the past the final piece of information returns with less damage.

Such an effect only works in quantum mechanics, in simulations conducted via quantum computers, because time travel is not yet possible.

“On a quantum computer, there is no problem simulating opposite-in-time evolution, or simulating running a process backwards into the past,” said Nikolai Sinitsyn, a theoretical physicist at Los Alamos National Laboratory, in a statement.

“We can actually see what happens with a complex quantum world if we travel back in time, add small damage, and return. We found that our world survives, which means there's no butterfly effect in quantum mechanics.”

To test the butterfly effect, the researchers used an IBM-Q quantum processor with quantum gates, which simulate forwards and backwards cause and effect.

Standard computers and processors use ‘bits’ in their chips, which exist in two positions - either ‘on’ or ‘off’ – which is the makeup of binary.

Quantum computers use ‘qubits’ rather than bits, which can be both be on and off simultaneously, as well as somewhere in between.

In the simulation, a person sends a qubit back in time. An intruder in the past measures the qubit, which disturbs it and changes its quantum correlations.

This is because even slight contact between an atom exhibiting quantum behaviour and another atom will immediately move the atom out of its quantum state.

The simulation is then run forward, to bring the qubit to the present day. It was found that, rather than the information being unrecoverable due to extrapolation of the small inciting incident – the act of stepping on a butterfly in the common metaphor – it was protected from minor tampering.

“We found that the notion of chaos in classical physics and in quantum mechanics must be understood differently,” Sinitsyn said.

The discovery could be used to hide information – converting it from its initial state into one of quantum entanglement – and could also be used to test quantum devices.

Since the lack of butterfly effect exists in quantum mechanics, if the simulation is run and the result is different it would prove that the quantum processor is not working effectively.