- Researchers design a theoretical method to improve quantum computing performance.
- The method is known as Dynamical Decoupling and it worked on 2 small-scale quantum computers.
- It doesn’t require encoding overhead and works by transforming quantum gates into decoupling pulse.
The concept of quantum computing was introduced in the early 1980s. The idea is to use quantum bits (qubits that can be in superpositions of states) instead of binary bits to perform calculations securely and at extremely fast speed.
Three decades later, the field of quantum computing is still in its infancy. Though hundreds of tests have been conducted in which quantum computations were executed on a small number of qubits.
Quantum computers are expected to be several million times faster than today’s supercomputers, and they have the potential to revolutionize finance, defense, information technology, and medicine industry. They utilize the behavior of atoms to perform incredibly complex tasks at extremely fast speeds.
They do however have some limitations. They are highly prone to error and require stability to sustain operations. Usually, they do not function properly and produce poor outcomes. Researchers all over the world still haven’t able to achieve a quantum machine that outperforms a traditional computer in any task.
The main issue with current quantum computers is ‘noise’ – disturbance caused by vibration, temperature, and sound. It generates decoherence, which can make qubits unstable by disrupting the duration of a quantum state. This decreases the time a quantum machine can accurately perform a task (with no errors).
A quantum machine with too much decoherence has no use. If you can solve this issue, you can reach to the point where quantum computing becomes practical and more productive than conventional computers.
Recently, researchers at the University of Southern California revealed a theoretical method to improve quantum computing performance. It addresses a weakness of current quantum computers by minimizing faulty calculations while escalating fidelity of outcomes. The method is known as Dynamical Decoupling (DD) and it worked on 2 quantum computers.
DD is developed to suppress decoherence through the application of pulses applied to the system, which cancel the interaction between system and environment to a given order in time-dependent perturbation theory. Overall, it does not require encoding overhead and works by transforming quantum gates into decoupling pulse.
The time sequences for these tests were very small: 200 pulses were recorded within 0.6 microseconds.
Applying Dynamic Decoupling In Today’s Quantum Machine
Researchers tested DD on 2 quantum computers — IBM’s 16-qubit QX5 and Rigetti’s 19-qubit Acorn — and they discovered that it’s easier and more reliable than other methods. It’s suitable for implementation in existing small-scale cloud-based quantum computers.
The 8-qubit quantum processor | Image credit: Rigetti Computing
The method can protect entangled two-qubit states to some extent. Different sequences of dynamic decoupling can mitigate both dephasing and spontaneous emission errors. Unlike previous studies, they didn’t use quantum error correcting code and thus achieved exceptional improvements in fidelity against natural decoherence.
The final fidelity for the IBM’s QX5 jumped from 28.9% to 88.4%, while for Rigetti’s Acron, it improved from 59.8% to 77.1%. The researchers also discovered that more pluses always enable fidelity improvements to sustain for longer duration in the Rigetti quantum computer, whereas for the IBM computer, there was a limit of approximately 100 pulses.
Overall, the study shows the dynamic decoupling mechanism works far better than existing quantum error correction techniques.