Today, IBM announced that it has signed a definitive agreement to acquire HRL Laboratories, a flagship research and development (R&D) institution pioneering breakthroughs in physical and information sciences, including quantum technologies.

We are extremely excited about this acquisition for its potential to accelerate and expand our quantum vision. IBM is a global leader in quantum computing, and we believe that HRL’s advanced expertise in silicon-spin qubit engineering will complement and extend our long-term mission to scale powerful quantum computers. We hope that HRL’s portfolio will help IBM push the frontiers of information technology in a quantum future, from future generations of quantum computers to a quantum computing internet capable of revolutionizing industries.

Superconducting qubits and spin qubits both leverage state-of-the-art silicon fabrication. This shared foundation is amongst the reasons why these two modalities offer the credible paths to scaling quantum technologies.

So, we wanted to give a brief overview of spin qubits and why we’re excited about this announcement.

What are spin qubits?

Part of our excitement surrounding HRL’s technology isn’t the differences between spins and superconducting qubits—but rather their similarities. Like superconducting qubits, spin qubits are fabricated on chips using typical chip fabrication technology. Both sit inside of cooling infrastructure, controlled via external signals applying gates to coupled qubits. The key difference is how we store and manipulate the quantum information itself.

Remember, quantum computers require that we can encode information into the states of a quantum system, and then manipulate those states in order to run calculations. Spin qubits rely on one of the most fundamental quantum states we can access: the spin of an electron. Particles carry an innate property named “spin” because it obeys mathematical equations that mirror the equations governing rotation on the large scale. But in the case of quantum computation, we mainly care that it’s a property we can use to represent the 0 and 1 of computation. Electrons all have a spin value of either positive or negative ½, also called “up” and “down.”

Spin offers us a property we need—then we need a way to control it. We do this using quantum dots, tiny structures which allow us to confine and control the properties of single electrons. HRL makes their quantum dots from SiGe, layers of silicon and germanium.

One could naively decide that “spin down is the qubit’s 0, spin up is the qubit’s 1,” but controlling single spins is extremely challenging, requiring precision engineering. HRL instead uses a qubit architecture called exchange only qubits where each qubit corresponds to three electrons stored in three quantum dots, called the exchange only qubit. Two of these electrons determine the computational 0 and 1—if the total spins of the electrons sum to 0, then the qubit is in the 0 state, and if they sum to 1, then the qubit is in the 1 state. The third qubit essentially acts to keep the whole system in check. Gates are applied as pulses of electricity that push electrons closer together or further apart.

What are the benefits of spin qubits?

Spin qubits can be manufactured using existing semiconductor fabrication tools, with the potential for manufacturability at scale. They further show high coherence times, low error rates, and are relatively easy to control. As they mature, we expect them to efficiently run large quantum circuits with low overhead. Finally, they can operate at 1K, versus superconducting qubit architectures which operate at .015K.

Where are we with spin qubits today?

Recently, HRL showed off a digitally controlled silicon-spin quantum computer using silicon to create manufacturable CMOS for both the qubit array and its cryogenic control board. This device features 54 quantum dots on three rails acting as a chip with up to 18 qubits. Their demonstrations showed the ability to run one- and two-qubit gates and small-scale error-detecting codes.

How do spin qubits play into IBM Quantum’s mission?

“The HRL team will help IBM push even farther forward toward the frontiers of quantum innovation,” said Jay Gambetta, IBM’s Director of Research and IBM Fellow. “This talented group of researchers brings a broad portfolio of technologies that will strengthen IBM's long-term plans to deliver useful quantum computing to the world, bringing together advances across quantum computing, quantum sensing, and quantum networking to enable the applications of the future.”   

How else will HRL work together with IBM?

IBM has historically focused on the computational powers of quantum technologies. HRL has developed other technologies that will amplify this bold plan, introducing quantum sensing and quantum networking into the portfolio. This includes ultra‑precise quantum sensors capable of detecting subtle physical phenomena and capturing finely tuned measurements for healthcare, navigation, defense, and scientific applications. Additionally, HRL maintains a bench of breakthroughs in novel quantum materials that could unlock more robust qubits, better semiconductors, and more sensitive sensors – all of which could improve the performance and scalability of future quantum computers and a wide range of quantum technologies.