An Introduction to Trapped Ion Quantum Computers

Quantum computing has the potential to revolutionize computing, outclassing even today’s fastest supercomputers. However, quantum computing is still on its way to being fully developed. In this development process, different types of quantum hardware are being researched to determine which is the best.

Quantum hardware can be assessed on 3 main criteria. The first criteria is how long hardware can maintain the state of quantum states created by quantum computers. The second criteria is the success rate of quantum gates on that hardware (also known as gate fidelity). Quantum gates are vital in quantum algorithms because they are transformations performed on a quantum state to produce the desired quantum state. The final criteria is the scalability of quantum computers using that harder. The easier to scale, the better the hardware.

The best quantum hardware would maintain the quantum states for the longest time possible while having a high success rate and being easily scalable (easy to build large quantum computers with more quantum bits, or qubits. However, the world isn’t perfect and this perfect qubit hasn’t been discovered yet. Instead, there are a few different types of qubits that are still being tested, one of which is the trapped ion qubit.

Trapped ion qubits are created by trapping ions in space using electromagnetic fields. Trapping these ions aims to isolate qubits from their surrounding environment to increase the amount of time quantum states are maintained. To further isolate ion trap qubits from the surrounding environment, the qubits are cooled to less than one one-thousandth of a degree above absolute zero. To apply gates on these qubits, lasers are used to create interference to change the quantum state of qubits.

When compared to other types of hardware, trapped ion qubits have both advantages and disadvantages. On one hand, trapped ion qubits have a higher gate fidelity compared to superconducting qubits and do not have limited gate connectivity, allowing qubits to interact with more neighboring qubits. Trapped ion qubits also maintain their quantum states for longer periods. On the other hand, the speed of gate manipulations on superconducting qubits is extremely fast, allowing more gates to be applied before a quantum state collapses. Additionally, it is harder to scale up trapped ion quantum computers compared to superconducting quantum computers.

Currently, companies and research institutes are still in the process of testing and improving the different quantum hardware. Many organizations are looking into ion trap quantum computers. Some of the main players include IonQ, Universal Quantum, and Honeywell each with its own success stories. For example, in October 2020, IonQ demonstrated extremely low gate error rates on a 32-qubit quantum computer. IonQ has also partnered with large companies like AWS (Amazon Web Services) to offer their quantum hardware for more widespread external use. Honeywell also recently announced that they had created a quantum system of 6 fully connected trapped ion qubits, meaning that these qubits are more efficient than other qubits that are not fully connected.

With the ongoing race to develop large-scale quantum computers, the best type of qubit is still being determined. Trapped ion qubits have the potential to be the main hardware of quantum computers in the future so it is important to understand some of this hardware’s key components, its current disadvantages, and its advantages over other competing technologies.

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