Quantum Correlations Fuel Thermodynamic Work and Detect Quantumness

Key Quotes

"the world that we know that we experience each day is what we call the classical world that is the familiar laws of physics apply the earth revolves around the sun because of gravity we can tell where a baseball is and measure how fast it's traveling a cup of hot coffee will eventually cool down let's focus on that cup of coffee for a second it's cooling down because of what we call the second law of thermodynamics which states that in an isolated system disorder will increase this is why heat flows from a hotter area to a colder one it's a fundamentally classical idea and it makes all the sense in the world"

This quote establishes the foundational understanding of the "classical world" and its governing principles, particularly the Second Law of Thermodynamics. The author, Samir Patel, explains that in our everyday experience, physical laws are predictable, and systems naturally tend towards greater disorder, exemplified by heat flowing from hot to cold. This sets the stage for contrasting these familiar concepts with the counterintuitive nature of quantum mechanics.

"what we can do with it is to create quantum equivalents of our classical devices like engines or like batteries because if we can use quantum correlations as a kind of fuel we could actually run a quantum engine on that and in fact this has been demonstrated basically with systems that are using individual atoms as though they are a kind of engine and it's been shown that in that case we can actually do work by burning up entanglements"

Phil Ball explains here how quantum correlations, specifically entanglement, can be harnessed as a form of "fuel." This allows for the creation of quantum devices, such as engines or batteries, that operate on principles not possible in the classical world. Ball highlights that this concept has moved beyond theory, with experiments demonstrating that individual atoms can function as engines powered by the "burning up" of entanglement.

"what these guys have shown it's really very neat that we can use this change to the second law of thermodynamics we can use that as a kind of witness for the quantumness in the system this is actually an idea that was over 20 years old that we could use thermodynamics as a witness of quantum entanglement by for example measuring some thermodynamic property of a quantum system technical things like the heat capacity how much heat it is required for it to increase in temperature and if we see something like that that is different from what classical thermodynamics would predict that might be an indication that there is quantumness there is entanglement in the system"

Phil Ball elaborates on a key application of quantum thermodynamics: using thermodynamic properties as a "witness" for quantum entanglement. He explains that by measuring certain thermodynamic characteristics of a system, such as its heat capacity, and observing deviations from classical predictions, scientists can infer the presence of quantum phenomena like entanglement. This approach offers a method to detect and confirm quantum behavior.

"all we now need to do is to get a thermometer and measure the temperature of this heat sink and we can tell whether there is entanglement in the system so we're getting experimental evidence that these theoretical devices are possible yeah in theory we can see how it should work and we're at the stage now particularly because we have quantum computers that we can manipulate and that we can monitor very closely we're at the stage where we can think about doing experiments like this"

Samir Patel summarizes the practical implications of the research discussed, emphasizing the role of a simple thermometer in detecting quantum entanglement. Patel notes that by measuring the temperature of a heat sink coupled to a quantum system, researchers can determine if entanglement is present, providing experimental evidence for theoretical concepts. He connects this to the current capabilities of quantum computing, suggesting that such experiments are becoming feasible.

"whenever you see google or ibm or whoever saying oh you know our quantum computer has just produced this result his first question is yeah but did it really do it with quantum how do we know for sure so that is a very practical question that's already confronting the quantum computer industry"

Samir Patel highlights a critical challenge facing the quantum computing industry: verifying the quantum nature of computations. He quotes a researcher who questions the validity of results claimed by major quantum computing companies, emphasizing the need for definitive proof that these machines are truly operating quantumly. Patel frames this as a pressing, practical concern for the industry.