IBM demonstrates ‘120x speedup’ in target quantum application

IBM has announced what it regards as breakthrough technology developments to improve how algorithms can run across classical and quantum computing platforms.

Like other organisations developing quantum computer technology, IBM said it had mostly focused on the execution of quantum circuits, or sequences of quantum operations. These operations run on IBM Quantum systems.

But some algorithms that use quantum computing require thousands, even millions, of interactions between quantum and classical computing architectures. To support this hybrid approach to computing, IBM said it was necessary to build systems that natively accelerate the execution of quantum programs, and not just quantum circuits.

“Systems built to execute quantum programs need to have significantly larger effective capacities, and they require improvements across the stack, including cloud service design, system software, control hardware, and even quantum hardware,” IBM researchers wrote in a blog post.

As an example of the types of problems a quantum computer could tackle, in 2017, Nature published an article by IBM’s Quantum team which demonstrated that a quantum computer could simulate the behaviour of the lithium hydride molecule. The paper was based on research using IBM’s 5-qubit system of 2017.

At the time, the authors of the paper said: “With future quantum processors, which will have more quantum volume, we will be able to explore the power of this approach to quantum simulation for increasingly complex molecules that are beyond classical computing capabilities. The ability to simulate chemical reactions accurately is conducive to the efforts of discovering new drugs, fertilisers, even new sustainable energy sources.”

In 2020, IBM laid out a roadmap detailing how it hopes to deliver systems with 1,121 qubits by 2023, for running quantum applications in natural sciences. At the time, its fastest offering was the 65-qubit IBM Quantum Hummingbird processor.

According to the blog post, the process of modelling the molecule described in the Nature paper would take 45 days when run on today’s quantum computing services. This is because there is a large latency as processing is passed back and forth between a classical and quantum processor. “Now, we can solve the same problem in just nine hours – a 120x speedup,” the IBM researchers stated in the blog post.

To achieve this, they said, IBM made algorithmic improvements to reduce the number of iterations of the algorithm required to receive a final answer by two to ten times. They said improvements in system software removed approximately 17 seconds per iteration and improved processor performance resulted in a 10 times decrease in the number of shots, or repeated circuit runs, required by each iteration of the algorithm. IBM said it also made improvements to the control systems.

According to the researchers, IBM’s Qiskit Runtime, a containerised service for quantum computers, delivered further performance gains.

“Rather than building up latencies as code passes between a user’s device and the cloud-based quantum computer, developers can run their program in the Qiskit Runtime execution environment, where the IBM hybrid cloud handles the work for them. New software architectures and OpenShift Operators allow us to maximise the time spent computing, and minimise the time spent waiting.”

IBM has now released the Qiskit Runtime.