The science behind Quantum Moves 2

Quantum Moves 2 is about quantum control and hybrid intelligence so let’s understand the science a bit deeper!

Quantum control is the complex task of controlling and manipulating a quantum system on very short timescales (typically less than a millisecond). The development of quantum optimal control is an essential requirement for future quantum technology. For example, the ability to control and manipulate single atoms form the building blocks of a quantum computer.

The quantum system that we want to control is a cloud of Rubidium87 atoms at ultra-cold temperatures to perform quantum computing and to create ‘atom lasers’.

Quantum Computing

The building blocks of a quantum computer are called qubits (quantum bits). In our experiment, the qubits are an array of individual atoms arranged in an optical lattice. You can think of an optical lattice as an egg-tray made out of light.

In the quantum lab, we use ultra-focussed laser beams called “optical tweezers” to ‘grab’ the atoms in the lattice. Have a look at the image below: the red tube is the light of an ultra-focussed laser, which can manipulate a single site in the optical lattice. Each “site” on the lattice (where atoms sit, and where an egg would sit in an egg carton) is about 500 nm away from the next site. This is equivalent to approximately 0.001 times of the width of a strand of hair. Every time a laser beam is focussed on a specific atom, the atom is trapped in the laser beam instead of the lattice. To make quantum calculations, we need to be able to grab one specific atom, move it around in the lattice and place it on top of another atom.

Atom Lasers

We also want to control a large group of atoms at ultracold temperatures known as Bose-Einstein Condensate (BEC). Imagine it as building an “atom freezer” capable of producing clouds of atoms with temperatures just above absolute zero. Absolute zero (-273 .15 deg C / −459.67 F / 0 Kelvin ) is the point at which there is absolutely no heat energy remaining to be extracted from the substance. These atoms behave a lot like photons in a laser, where they behave like particles and “matter” waves at the same time. Because of this, some researchers refer to BECs as the atom analog of a laser. As a result of this interesting behavior, ultracold atom-based sensors could be millions of times more sensitive than current technologies based on light! This opens up the fascinating world of quantum matter-wave optics in quantum technology and paves the way for the next generation of sensors, clocks, and other useful tools.

In general, every time you play Quantum Moves, you create a solution which appears on our end as data describing the movement of the laser beam and how the atoms respond.

Primary gameplay elements

In the game, you will encounter five primary elements:

  1. A ‘sloshy liquid’: The liquid-like material that you will be playing within the game is a simulation of ultracold atoms. In physics, we call the liquid a “wavefunction” because of the wave-like nature of these quantum objects.
  2. Moving the atoms (sloshy liquid) with the optical tweezer:
    Remember that we move our atoms with the help of our optical tweezer (the ultra-focussed laser light tube shown in the images above). Left and right mouse movements correspond to real movement of the laser, while by moving the mouse up and down, you can increase and decrease the intensity of the laser (and the depth of the “well” that the atoms see). Every blue dot that you see on the screen is a re-trace of your mouse movements. This data is then sent to the quantum engine to describe the movement and intensity of the laser.
  3. Find the best solution: In order to obtain a good solution, we need the “overlap” of the initial and target shapes to be high. This overlap, or similarity, between the two states, is measured by a quantity called ‘Fidelity’. We define our “fidelity” so that the best possible solutions have a fidelity equal to one The best way to move the atoms is usually done with the least “sloshing,” just like when you are trying to move a full cup of hot coffee from one room to another! When the atoms “slosh” about in the optical tweezer, it means that you have added too much energy to the system and excited them. Excited atoms don’t like to stay in the laser well, so we try to keep the atoms as calm as possible.
  4. Time Limit: all levels must be completed within a few seconds. Our atoms don’t stay in the tweezer forever, so we need to be able to move them quickly. The faster we can move the atoms around in the tweezer, the better our final sensor, quantum computer, or clock can be! Therefore, the race is on to get the best solutions in the least amount of time!
  5. Optimize your solution:
    When you have a solution that you like, you can try and optimize it. The quantum engine will then analyze your solution and try to make it even better! The optimization tool is started by clicking the ‘Optimizer’ switch in the game. You will be able to see directly how the initial solution is modified by the optimization tool and how the final shape of the liquid adapts to the target shape. Along with this, you will also see your fidelity rise. You can click on the optimization switch at any time to stop it. By looking at how the computer optimizes your solution, you can even generate new solutions that are even better than the ones you could make before!

It is very difficult to formalize how humans think about different types of solutions, and this thinking can vary greatly from one problem to another. When scientists try to solve these research problems, we have to use our intuition to make some guesses about what makes a good solution. A "good" solution is a solution that gives a high fidelity when optimized. Finding these good guesses can be very complicated, and it is very difficult to tell a computer exactly what to do. Therefore, we are trying to rely on the player’s human intuition combined with our optimization tool. With this hybrid intelligence, we hope to understand if humans can provide good results when compared to our conventional methods.

Science behind Quantum Moves 2