Atomtronics: researchers shine a light on post electronics

Most modern technologies owe their success to advances in electronics. Now researchers are starting to explore atomtronics: ways to harness the flow of waves of whole atoms, called matter waves, to enable new kinds of sensors, computers, and scientific research.

Prof. Luigi Amico, Executive Director of Quantum Physics at the TII Technology Innovation Institute in the United Arab Emirates, explains why we are on the brink of entering a “second quantum revolution.”

Most technology advancements over the last century arose from the understanding that elementary particles like electrons, protons and photons obey the rules of quantum physics.

Electronic devices such as TVs, computers, cellphones, and the internet, are all offshoots of this first quantum revolution developed at the turn of the century.

Today, we are in the wave of a second quantum revolution arising from a deeper understanding of the collection of elementary quantum particles.  For such composite systems, a  phenomenon known as entanglement can take place. A characteristic trait of such a revolution, called Quantum Technology, is that basic and applied research work are shortcut which means that physics principles and technological applications are tightly intertwined.

The bulk of existing quantum computer research rests on classical hardware that manipulates currents of electrons. Therefore, it is only natural and beneficial to switch to true quantum hardware that can take advantage of more types of elementary particles.

Atomtronics is the quantum technology of atomic matter-wave circuits. The physics principles exploited in atomtronic circuits are very different compared to the ones which govern electronics. Therefore, devices with radically new functionalities and performances are expected to be accessed.

One goal is to work out new quantum devices and a new concept of circuitry. At the same time, atomtronics can define current-based quantum simulators exploiting matter-wave motion to advance fundamental science. This field is still young but mastering this new realm could unlock vast improvements in sensing, computation, and communication.

It took several decades to develop quantum theory into practical devices like televisions, lasers, and semiconductor chips.  We want to shorten this gap for the next quantum revolution and control whole quantum aggregates in which entanglement can occur. Atomtronics harnesses the core principles of quantum technology. In comparison to other systems, atomtronic circuits stand out by their enhanced and dynamical flexibility and their superb control of operating conditions.

The goal of atomtronic is to fabricate circuits of atoms.  In a very crude representation, a traditional circuit is made by electrons moving in copper wires.  In atomtronics, electrons are replaced by atoms and the copper wires are substituted by a suitable combination of laser and magnetic fields which guide the atoms. In the implementations achieved so far, the fluids of moving atoms are kept at very low temperatures (in the range of hundreds of Nanokelvins).

In these conditions, besides their mass, atoms have very different properties from electrons. The atomic spin becomes a key quantity.  The laser light ‘copper wires’ for atomtronic circuits provide very smooth guides for the atoms, and circuits of virtually any shape can be realized.

This allows researchers to consider new ways of harnessing matter waves into circuits with different characteristics than existing electronic circuits.

Another important difference between standard electronic and atomtronic circuits tracks back to the electrical charge of the carriers. Electrons are electrically charged, which makes them easy to manipulate using electrical and magnetic fields. For the very same reason, however, electrical currents can be distracted in many ways since electrons are easily affected by circuit imperfections and/or spurious effects (leading to an essential unwanted phenomenon for quantum technology known as decoherence, which destroys useful entanglement).

 In contrast, atoms flowing in atomtronic circuits are electrically neutral. This feature means that more sophisticated methods are required to manipulate them. It also means they are easier to isolate and less prone to decoherence.  

Potential applications

Improved sensors could be one of the most promising applications in the short run. For example, today, photon-based gyros allow us to measure rotations accurately. These devices can lead to high-end inertial sensors which can be used for autonomous vehicles which navigate without using GPS signals. Atomtronic gyros are expected to maintain accuracy over more extended functioning periods and promise a substantial increase of sensitivities compared to photonics gyros.

Atomtronic rotation sensors could unlock new research opportunities.  For example, geophysicists have discovered that, in the classifications of earthquakes, minute rotational changes can provide even more insight than simply measuring spatial displacement as the standard seismographs currently do. These movements can be in the range of 10^-7 –  10^-11 radians per second. Imagine you are rotating at 10^-11 radians per second. It would take you longer than 30 thousand years to complete one full revolution. The corresponding sensitivity for detecting such a small rotation is hard, if not impossible, to be achieved with existing quantum sensors, but we believe it will be possible to construct sensors to detect this level of rotation with atomtronics.

Atomtronics could also help define scalable integrated 3-dimensional complex matter-wave circuits. Traditional semiconductor circuits are composed of a 2D substrate laid out on a plane. Engineers paint lines into this circuit to create transistors, gates, and more complex logical circuits. With atomtronics, people are working on 3D circuits that can be dynamically reconfigured.

A significant challenge to face in the years to come is integrating the atomtronic circuits with other existing technologies such as photonic integrated circuits. Such hybrid networks may provide a valuable route for the fabrication of integrated 3D matter-wave circuits.  

The most popular quantum computer designs today are built using superconducting electronic circuits. In the long term, atomtronics can be a good platform for quantum computers based on atomic motion.

We are making progress in reconfigurable atomtronic circuits. The wires in an electronic circuit are permanently fixed. You can use switches to route currents down different routes, but the actual wires remain. New atomtronic designs mean circuits can be re-shaped while the circuit operates. Because of such features, atomtronic circuits can be manipulated by new ‘analogic’ methods such as machine learning algorithms.

This way, circuital elements with exotic ‘current-voltage’ characteristics can be defined.  This route can lead to new circuit elements that cannot be accessed with standard electronics.

For example, atomtronics could contribute to the mesoscopic quantum technology realm between the microscopic domain of atoms and the macroscopic field of falling apples. It would allow researchers to extend mesoscopic research beyond studying static electronic circuits to also consider other dynamic circuits that include other types of particle flows.

The bulk of knowledge acquired so far indicates that the current is a very effective probe to explore the microscopic behavior of the phases of matter at low temperature.

We are exploring ways to exploit atomtronic circuits as simulators to address important partially open questions in high energy physics, such as quantum gravity, meson scattering, and quark-gluon plasmas.

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Atomtronics is an extremely collegiate and open global world community in which any progress in the field is shared intensely.  This feature is a characteristic trait of the physicist community, and we are optimistic and excited about the advancing the next revolution with colleagues worldwide.

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