To mitigate the invariable consequence of entropy in precise timekeeping, scientists developed a new kind of quantum clock that tracks overall flow of time without interruption, instead of measuring each individual tick.
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To mitigate the invariable consequence of entropy in precise timekeeping, scientists developed a new kind of quantum clock that tracks overall flow of time without interruption, instead of measuring each individual tick.
An illustration showing a virtual clock.
For years, physicists have been trying to design clocks that can measure tiny durations of time with extreme precision. Quantum clocks, in particular, have pushed the boundaries by using the strange rules of quantum mechanics to achieve mind-boggling accuracy.
However, there has always been a catch: the more precise these clocks get, the more energy they burn and the more disorder or entropy they create. This has long been seen as an unavoidable cost of keeping precise time.
Now, a team of international researchers has challenged this belief. They’ve developed the framework for a new type of quantum clock that can tick with remarkable precision while wasting much less energy.
This research could fundamentally change how we build clocks and might lead to more efficient quantum computers and related technologies.
The idea for this new kind of clock came out of a meeting at the Quantum Thermodynamics Conference in Vienna in 2023. Researchers wanted to rethink the basic assumptions behind timekeeping at the quantum level.
Traditional clocks, including quantum ones, rely on counting repeated, irreversible events, like a pendulum swinging or atoms jumping between energy levels. Every time one of these ticks happens, a small amount of energy is lost as heat—that’s entropy.
In classical and most existing quantum clocks, if you want to double the precision, you have to double the entropy produced. This one-to-one trade-off has been considered a fundamental limitation until now.
To mitigate this, the researchers proposed a different strategy. Instead of treating each tick as a separate event that must be observed and recorded (thus dissipating energy), they studied what would happen if one could let quantum events unfold coherently, smoothly, like a wave, without disturbance.
In their model, the clock doesn’t measure each individual tick. Instead, it tracks the overall flow of time by letting quantum excitations (tiny packets of energy) move across a system without interruption. This is known as coherent quantum transport.
“The main principle is the possibility to trade off a clock’s precision with its resolution (in a new and genuinely quantum manner). Like in an hourglass, we can, instead of using individual sand grains as ticks, wait until a sufficient quantity has fallen through. The resulting time units will be resolved more precisely, at the expense of having to wait longer,” Marcus Huber, one of the researchers, told Tech Xplore.
In mechanical clocks, you might imagine the second hand quietly moving without anyone watching, yet still moving the minute hand forward. The same logic applies here. Since there’s no measurement or disturbance during the intermediate steps, the system avoids producing entropy with every tick.
This approach has a powerful effect. The relationship between precision and entropy is no longer linear. Instead of needing to double the entropy to double the precision, now entropy only grows slowly as precision improves. That’s a huge efficiency gain.
The clock design proposed by the researchers is based on quantum many-body systems, where particles behave in coordinated, wave-like patterns. This kind of collective behavior allows for precise control without the usual thermodynamic cost.
The researchers used theoretical models to confirm this idea, and now they are beginning to build real versions. For instance, at Chalmers University of Technology in Sweden, a team is working on a prototype using superconducting circuits.
This breakthrough could be a big step forward in precision timekeeping, especially as we develop more advanced quantum technologies. Currently, energy dissipation isn’t a major problem for the most advanced atomic clocks, but that’s likely to change.
“A useful analogy comes from classical computing: for many years, heat dissipation was considered negligible, but in today’s data centers that process vast amounts of information, it has become a major practical concern. In a similar way, we anticipate that for certain applications of high-precision clocks, dissipation will eventually impose limits,” Florian Meier, lead researcher, said.
The proposed approach doesn’t eliminate entropy entirely. That would be a violation of the laws of thermodynamics. However, it does show that we can reduce it to a great extent, using clever quantum effects like coherent transport.
This achievement isn’t just limited to precise timekeeping. For instance, these nearly dissipation-free processes could be used to run other quantum machines, like sensors or processors, in a more energy-efficient way.
Next, the researchers plan to test their clock design in real-world lab settings. The prototype being built at Chalmers will help demonstrate whether the theoretical energy-saving advantages hold up in practice.
The study is published in the journal Nature Physics.
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Source: Interesting Engineering
