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Quantum State Assembler

Periodic Reporting for period 2 - QuStA (Quantum State Assembler)

Reporting period: 2018-10-01 to 2020-03-31

In our modern world we use a large number of materials with exotic properties that cannot easily explained by looking at their constituents. Quantum correlations are at work and understanding the reason for interesting macroscopic behavior is often elusive. QuStA tries to build model materials starting from basic building blocks to decipher key mechanisms. This might help researchers to establish new strategies to find – or fine tune – materials with new properties.
The first success towards this goal is the observation how a very important phenomenon observed in materials arises as the particle number is increased: Because the interactions between the constituting atoms can be tuned very simply by applying a magnetic field QuStA could observe how as system of up to 12 trapped atoms transitions from one with normal conducting properties to one where transport is possible without any resistance. The precursor of a phase transition between a normal- and a superfluid was observed.
To test what is exactly the mechanism behind this phase transition, the researchers started to look into the correlations that might be responsible, for which they had to devise a new method to detect each and every single particle. To test this method, they used it on a system of noninteracting fermionic atoms, which obey the Pauli principle also known from chemistry. As of these particles only one can occupy a quantum state at a time. This is how they form what is called a Pauli crystal, even though there is literally no interaction between them. QuStA could for the first time observe such a crystal.
A lot of interest has been created recently about controlling and manipulating quantum states for the use in quantum computation and simulation. While the number of particles currently employed by QuStA are not as large as in other systems, one major advantage is that due to its unique approach, it can prepare systems in a state where all degrees of freedom are controlled. In this way, already with 12 particles, QuStA is currently the limit of what can be modelled on a conventional computer.