Paul is President of Quantum Computing at ColdQuanta, where he leads the team building the world’s most useful quantum computer.
Timbuk3 was a one-hit-wonder band, best known for their 1986 song “The Future’s So Bright.” As a high school student planning to major in Physics at college, the lyrics “I study nuclear science, I love my classes, the future’s so bright, I gotta wear shades” was a fun affirmation for my chosen field of study. Thirty-five years later, that song comes back to mind as we face a tremendously bright future for the field of cold atom technology.
Atoms are nature’s building blocks and while in large numbers they act in macroscopic fashion, when isolated and cooled down, their quantum nature comes to the forefront. In fact, in gaseous form at room temperature, atoms are buzzing around at over 1,000 mph. Heat is simply motion energy, so if you can slow atoms down to a crawl, their quantum properties can be manipulated and utilized.
Timbuk3 clearly had great prescience: Just a year after this song’s release, David Pritchard and Steven Chu first trapped atoms in a magneto-optical trap (or MOT) at Bell Labs, laying the foundation for the cold atom revolution to follow. In 1995, Eric Cornell and Carl Wieman at the University of Colorado, Boulder, created the first Bose-Einstein Condensate, a form of matter in which atoms are cooled down to just a few hundred nano-Kelvin, behaving as a single quantum ground state object rather than individual atoms.
This trapping and cooling of atoms enables a broad range of use cases that are on the cusp of delivering transformational impact across multiple industries.
The most significant initial application is in delivering more accurate atomic clocks, which are the backbone of modern industry — from telecommunications and financial services to energy distribution. Cold atom technology will enable clocks that deliver several orders of magnitude improvement in reliability and lower cost and in a dramatically reduced form factor compared to existing state-of-the-art atomic clocks.
More generally, cold atoms take on different functionality based on configuration. A sophisticated 3D shaken lattice configuration can enable extremely sensitive accelerometer, gyroscope and gravimetry capabilities. Coupled with an ultra-precise cold atom clock, this functionality will enable Quantum Positioning Systems (QPS) that provide precision navigation and timing without the need for ongoing external frames of reference. Most of the world relies on GPS for navigation, but GPS can be spoofed or denied and the signal can be lost easily. With the ability to offer centimeter-level accuracy for days without external reference, QPS systems will have a revolutionary impact on broad fields including autonomous vehicles, transportation and defense.
Cold atoms that are excited into high Rydberg states, in which the valence electron is far from the nucleus, are extremely polarizable which makes them highly sensitive to electromagnetic fields. Rydberg atoms can be used as the basis of an extremely sensitive radio frequency (RF) sensor across a wide swath of electromagnetic spectrum. These sensors are hundreds to thousands of times more sensitive than conventional antenna technologies. This opens up exciting new horizons in communications, remote sensing and defense applications.
Perhaps the most exciting application of cold atoms is in quantum computing. The ultimate goal for quantum computing is to reach quantum advantage — the point at which a quantum computer can achieve an exponential speed up of a useful algorithm compared to a classical computer. This will require hundreds of thousands, or perhaps millions, of qubits (quantum bits).
Atoms are essentially nature’s qubit. Every atom of a given element is pristine and exactly the same. They don’t require an expensive fab to manufacture, and they aren’t subject to manufacturing defects or failures. This makes cold atom qubits inherently scalable to very large qubit counts. Because they are neutral, atoms can be packed together very closely in the quantum processing unit (QPU) with separations of just a few microns. In this configuration, 1 million qubits would fit on a fingernail with plenty of room to spare. It’s conceivable that a large-scale quantum computer based on cold atoms could fit into a simple rack-mountable unit.
In a seeming paradox, atoms trapped with lasers can be cooled to micro-Kelvin temperature within the QPU without cryogenics or other refrigeration — further supporting the inherent scalability of this approach.
The quantum mechanical aspects of Rydberg atoms have powerful benefits for creating a quantum computer. Entanglement between qubits, an important aspect of most quantum computations, is enabled through the Rydberg blockade mechanism, which enables distant qubits to be entangled. This was first demonstrated in pioneering work done in 2009 by Mark Saffman and Thad Walker at the University of Wisconsin-Madison. The physics of the blockade mechanism leads to large-scale connectivity, which is critical to error reduction (a critical issue in quantum computing) and to the implementation of complex quantum circuits.
A key issue in quantum computing is the fact that qubits are highly sensitive to their environment and can very quickly lose their quantum state through a process known as decoherence. However cold atom qubits are very stable, exhibiting coherence times that can ultimately scale to many seconds, which is eight orders of magnitude longer than the corresponding gate operation times. In other words, coherence time is not an issue for cold atom-based quantum computers.
This combination of qubit count scalability, qubit fidelity and connectivity means that cold atoms are the most promising approach for building a quantum computer that can achieve quantum advantage. Interestingly, many of the same factors that enable this scale also support miniaturization. By the end of this decade, we may see cold-atom quantum computers deployed in data centers, as part of telecommunication networks, field-deployed on vehicles and perhaps even in orbit on satellites.
We are at a pivotal point in the evolution of the quantum technology market, driven by a combination of scientific breakthroughs, engineering advancements and academic research. Timbuk3 summed up the bright future for cold atom technology in their lyrics, “Things are going great, and they’re only getting better.” Time to buy a new pair of shades!