The Entropy of Quantum Entanglement

Bartosz Regula from the RIKEN Center for Quantum Computing and Ludovico Lami from the University of Amsterdam have shown, through probabilistic calculations, that there is indeed, as had been hypothesized, a rule of entropy for the phenomenon of quantum entanglement.


This finding could help drive a better understanding of quantum entanglement, which is a key resource that underlies much of the power of future quantum computers. Little is currently understood about the optimal ways to make effective use of it, despite it being the focus of research in quantum information science for decades.


The second law of thermodynamics, which says that a system can never move to a state with lower entropy, or order, is one of the most fundamental laws of nature, and lies at the very heart of physics. It is what creates the "arrow of time," and tells us the remarkable fact that the dynamics of general physical systems, even extremely complex ones such as gases or black holes, are encapsulated by a single function, its entropy.     READ MORE...

Time Reversal

A team of researchers from the University of Twente has successfully illustrated that quantum mechanics and thermodynamics can coexist by using an optical chip with photon channels. The channels individually showed disorder in line with thermodynamics, while the overall system complied with quantum mechanics due to the entanglement of subsystems, proving that information can be preserved and transferred. Credit: University of Twente

It seems quantum mechanics and thermodynamics cannot be true simultaneously. In a new publication, University of Twente researchers use photons in an optical chip to demonstrate how both theories can be true at the same time.

In quantum mechanics, time can be reversed and information is always preserved. That is, one can always find back the previous state of particles. It was long unknown how this could be true at the same time as thermodynamics. 

There, time has a direction and information can also be lost. “Just think of two photographs that you put in the sun for too long, after a while you can no longer distinguish them,” explains author Jelmer Renema.

There was already a theoretical solution to this quantum puzzle and even an experiment with atoms, but now the University of Twente (UT) researchers have also demonstrated it with photons. “Photons have the advantage that it is quite easy to reverse time with them,” explains Renema. 

In the experiment, the researchers used an optical chip with channels through which the photons could pass. At first, they could determine exactly how many photons there were in each channel, but after that, the photons shuffled positions.  READ MORE...

Time Crystal

Google’s quantum computer has been used to build a “time crystal” according to freshly-published research, a new phase of matter that upends the traditional laws of thermodynamics. 

Despite what the name might suggest, however, the new breakthrough won’t let Google build a time machine.

Time crystals were first proposed in 2012, as systems that continuously operate out of equilibrium. Unlike other phases of matter, which are in thermal equilibrium, time crystals are stable yet the atoms which make them up are constantly evolving.

At least, that’s been the theory: scientists have disagreed on whether such a thing was actually possible in reality. Different levels of time crystals that could or could not be generated have been argued, with demonstrations of some that partly – but not completely – meet all the relevant criteria. 

In a new research preprint by researchers at Google, along with physicists at Princeton, Stanford, and other universities, it’s claimed that Google’s quantum computer project has delivered what many believed impossible. 

Preprints are versions of academic papers that are published prior to going through peer-review and full publishing; as such, their findings can be challenged or even overturned completely during that review process. READ MORE