Small Time Arrow

Time runs forward
Time runs forward

The onward march of time is widely considered to be underwritten by the Second Law of Thermodynamics, which describes the tendency of a system to increasing disorder. Apparently there have been doubts that this applies at a quantum level where theoretically time could equally run backwards.

However PhysicsWorld reassuringly reports that time probably runs forward even at the quantum scale. I can’t pretend to understand the intricacies of the experiment described here, but I am relieved at the results. The experiment …

… involves coupling a superconductor qubit to the fundamental mode of a microwave waveguide cavity. With this setup, the researchers can determine the quantum state of the qubit by measuring the phase of the cavity’s output signal. Because of the quantum nature of the system, the measurement results in a backaction that affects the final state of the qubit.

I hoped other science blogs might have reported the good news (and perhaps in layman’s terms), but a cursory web search revealed nothing, other than that perhaps it’s not “new” news. Back in 2015, the excitingly named ScienceAlert reported the same results from a different experiment in which …

… the researchers used a bunch of carbon-13 atoms in liquid chloroform, and flipped their nuclear spins using an oscillating magnetic field. 

Again, the details of the process mean nothing to me, but the comforting assurance remains: all is well with reality.