Quantum experiments all the time should cope with the identical problem, no matter whether or not they involve quantum computers, quantum teleportation or latest kinds of quantum sensors: quantum effects break down very easily. They’re extremely sensitive to external disturbances — for instance, to fluctuations caused just by the encompassing temperature. It’s subsequently vital to have the ability to chill down quantum experiments as effectively as possible.
At TU Wien (Vienna), it has now been shown that one of these cooling might be achieved in an interesting latest way: A Bose-Einstein condensate is split into two parts, neither abruptly nor particularly slowly, but with a really specific temporal dynamic that ensures that random fluctuations are prevented as perfectly as possible. In this fashion, the relevant temperature within the already extremely cold Bose-Einstein condensate might be significantly reduced. This is essential for quantum simulators, that are used at TU Wien to achieve insights into quantum effects that would not be investigated using previous methods.
Quantum simulators
“We work with quantum simulators in our research,” says Maximilian Prüfer, who’s researching latest methods at TU Wien’s Atomic Institute with the assistance of an Esprit Grant from the FWF. “Quantum simulators are systems whose behavior is set by quantum mechanical effects and which might be controlled and monitored particularly well. These systems can subsequently be used to review fundamental phenomena of quantum physics that also occur in other quantum systems, which can’t be studied so easily.”
Which means that a physical system is used to truly learn something about other systems. This concept isn’t entirely latest in physics: for instance, you can too perform experiments with water waves as a way to learn something about sound waves — but water waves are easier to watch.
“In quantum physics, quantum simulators have change into an especially useful and versatile tool in recent times,” says Maximilian Prüfer. “Amongst crucial tools for realizing interesting model systems are clouds of extremely cold atoms, corresponding to those we study in our laboratory.” In the present paper published in Physical Review X, the scientists led by Jörg Schmiedmayer and Maximilian Prüfer investigated how quantum entanglement evolves over time and the way this might be used to attain a fair colder temperature equilibrium than before. Quantum simulation can also be a central topic within the recently launched QuantA Cluster of Excellence, through which various quantum systems are being investigated.
The colder, the higher
The decisive factor that sometimes limits the suitability of such quantum simulators at present is their temperature: “The higher we cool down the interesting degrees of freedom of the condensate, the higher we are able to work with it and the more we are able to learn from it,” says Maximilian Prüfer.
There are alternative ways to chill something down: For instance, you may cool a gas by increasing its volume very slowly. With extremely cold Bose-Einstein condensates, other tricks are typically used: essentially the most energetic atoms are quickly removed until only a set of atoms stays, which have a reasonably uniformly low energy and are subsequently cooler.
“But we use a totally different technique,” says Tiantian Zhang, first writer of the study, who investigated this topic as a part of her doctoral thesis on the Doctoral College of the Vienna Center for Quantum Science and Technology. “We create a Bose-Einstein condensate after which split it into two parts by making a barrier in the center.” The variety of particles which find yourself on the suitable side and on the left side of the barrier is undetermined. As a consequence of the laws of quantum physics, there may be a certain quantity of uncertainty here. One could say that either side are in a quantum-physical superposition of various particle number states.
“On average, exactly 50% of the particles are on the left and 50% on the suitable,” says Maximilian Prüfer. “But quantum physics says that there are all the time certain fluctuations. The fluctuations, i.e. the deviations from the expected value, are closely related to the temperature.”
Cooling by controlling the fluctuations
The research team at TU Wien was capable of show: neither an especially abrupt nor an especially slow splitting of the Bose-Einstein condensate is perfect. A compromise should be found, a cleverly tailored approach to dynamically split the condensate, as a way to control the quantum fluctuations in addition to possible. This can’t be calculated: this problem can’t be solved using conventional computers. But with experiments, the research team was capable of show: The suitable splitting dynamics might be used to suppress the fluctuation within the variety of particles, and this in turn translates into a discount the temperature that you desire to minimize.
“Different temperature scales exist concurrently in this technique, and we lower a really specific one among them,” explains Maximilian Prüfer. “So you may’t consider it like a mini-fridge that gets noticeably colder overall. But that is not what we’re talking about: suppressing the fluctuations is strictly what we’d like to have the ability to make use of our system as a quantum simulator even higher than before. We will now use it to reply questions from fundamental quantum physics that were previously inaccessible.”
