Related Experiment Video
Updated: Jan 9, 2026
09:23
Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
Published on: May 30, 2014
15.0K
Entropic Costs of Extracting Classical Ticks from a Quantum Clock
Vivek Wadhia1, Florian Meier2, Federico Fedele1
1University of Oxford, Department of Engineering Science, Parks Road, Oxford OX1 3PJ, United Kingdom.
Physical Review Letters
|November 30, 2025
Summary
We built a quantum clock using charge tunneling in a double quantum dot (DQD). Measuring the entropy of the readout amplified precision, revealing the true thermodynamic cost of quantum timekeeping.
Area of Science:
- Quantum physics
- Thermodynamics
- Quantum information science
Background:
- Quantum clocks offer high precision timekeeping.
- Understanding the thermodynamic costs of quantum systems is crucial.
Purpose of the Study:
- To experimentally realize a quantum clock using charge tunneling.
- To investigate the thermodynamic cost of microscopic tick generation and macroscopic recording.
- To explore the interplay between quantum clockwork entropy and measurement apparatus.
Main Methods:
- Utilized a charge sensor to count tunneling events in a double quantum dot (DQD) as clock ticks.
- Measured power dissipation of the DQD and charge sensor in DC and RF modes.
- Analyzed the thermodynamic cost of both microscopic tick creation and macroscopic recording.
Main Results:
- Demonstrated that the measurement apparatus's entropy production significantly exceeds the clockwork's.
- Showcased that enhanced precision is achieved by exploiting the measurement record, even at equilibrium.
- Identified measurement-related entropy as the dominant thermodynamic cost in quantum timekeeping.
Conclusions:
- The entropy produced by amplification and measurement is the fundamental thermodynamic cost of quantum timekeeping.
- Macroscopic measurement significantly impacts and improves quantum clock precision.
- This work provides a microscopic understanding of the thermodynamic limits of timekeeping.
Related Concept Videos
02:45The Quantum-Mechanical Model of an Atom
56.4K
Shortly after de Broglie published his ideas that the electron in a hydrogen atom could be better thought of as being a circular standing wave instead of a particle moving in quantized circular orbits, Erwin Schrödinger extended de Broglie’s work by deriving what is now known as the Schrödinger equation. When Schrödinger applied his equation to hydrogen-like atoms, he was able to reproduce Bohr’s expression for the energy and, thus, the Rydberg formula governing hydrogen spectra.
56.4K
01:20Entropy and the Second Law of Thermodynamics
4.7K
The second law of thermodynamics can be stated quantitatively using the concept of entropy. Entropy is the measure of disorder of the system.
The relation between entropy and disorder can be illustrated with the example of the phase change of ice to water. In ice, the molecules are located at specific sites giving a solid state, whereas, in a liquid form, these molecules are much freer to move. The molecular arrangement has therefore become more randomized. Although the change in average...
The relation between entropy and disorder can be illustrated with the example of the phase change of ice to water. In ice, the molecules are located at specific sites giving a solid state, whereas, in a liquid form, these molecules are much freer to move. The molecular arrangement has therefore become more randomized. Although the change in average...
4.7K
01:10Entropy Change in Reversible Processes
3.2K
In the Carnot engine, which achieves the maximum efficiency between two reservoirs of fixed temperatures, the total change in entropy is zero. The observation can be generalized by considering any reversible cyclic process consisting of many Carnot cycles. Thus, it can be stated that the total entropy change of any ideal reversible cycle is zero.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.
3.2K
01:18Entropy
3.4K
The first law of thermodynamics is quantitatively formulated via an equation relating the internal energy of a system, the heat exchanged by it, and the work done on it. A quantitative formulation of the second law of thermodynamics leads to defining a state function, the entropy.
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
3.4K
03:00Standard Entropy Change for a Reaction
23.9K
Entropy is a state function, so the standard entropy change for a chemical reaction (ΔS°rxn) can be calculated from the difference in standard entropy between the products and the reactants.
23.9K
04:08The Uncertainty Principle
31.2K
Werner Heisenberg considered the limits of how accurately one can measure properties of an electron or other microscopic particles. He determined that there is a fundamental limit to how accurately one can measure both a particle’s position and its momentum simultaneously. The more accurate the measurement of the momentum of a particle is known, the less accurate the position at that time is known and vice versa. This is what is now called the Heisenberg uncertainty principle. He...
31.2K