Quantinuum doubles quantum volume of its computer

Technology News |
By Nick Flaherty

Anglo-America quantum company Quantinuum has doubled the performance of its quantum computing system for the second time in a year.

It has boosted the quantum volume of its trapped ion System Model H1 computer, developed by backer Honeywell, to 8192.

Quantum volume is a metric established by IBM in 2019 to measure the performance of quantum processors using randomized circuits in the NISQ (Noisy intermediate-scale quantum) region. This is a measure of the number of ways qubits can be combined, rather than the number of qubits available.

“We are making significant progress with both our hardware and software, in addition to building a community of developers who are using our TKET SDK,” said Tony Uttley, chief operating officer of Quantinuum.

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A key to achieving this new capability is directly implementing arbitrary angle two-qubit gates. For many quantum circuits built on trapped ions, this new way of doing a two-qubit gate allows for more efficient circuit construction and leads to higher fidelity results. 

“This new capability allows for several user advantages. In many cases, this includes shorter interactions with the qubits, which lowers the error rate. This allows our customers to run long computations with less noise,” said Dr. Brian Neyenhuis, Director of Commercial Operations at Quantinuum.

Researchers working with machine learning algorithms, variational algorithms, and time evolution algorithms would see the most benefit from these new gates. This advancement is particularly relevant for simulating the dynamics of other quantum systems. 

“With the quantum-charged coupled device (QCCD) architecture, interactions between qubits are very simple and can be limited to a small number of qubits which means we can precisely control the interaction and don’t have to worry about additional crosstalk,” said Neyenhuis.  

Currently, researchers can do single qubit gates or a fully entangled two-qubit gate. Arbitrary angle gates allow partial entanglement.

“There are many algorithms where you want to evolve the quantum state of the system one tiny step at a time. Previously, if you wanted a tiny bit of entanglement for some small time step, you had to entangle it all the way, rotate it a little bit, and then unentangle it almost all the way back,” said Neyenhuis. “Now we can just add this tiny little bit of entanglement natively and then go to the next step of the algorithm.”

There are other algorithms where this arbitrary angle two-qubit gate is the natural building block, according to Neyenhuis. One example is the quantum Fourier transform. Using arbitrary angle two-qubit gates cuts the number of two-qubit gates (and the overall error) in half, drastically improving the fidelity of the circuit. Researchers can use this new gate design to run harder problems that resulted in catastrophic errors in previous experiments.

“By going to an arbitrary angle gate, in addition to cutting the number of two-qubit gates in half, the error we get per gate is lower because it scales with the amplitude of that gate,” he said. 

This is a powerful new capability, particularly for NISQ algorithms.

“For the algorithms that we are going to want to run in this NISQ regime that we’re in right now, this is a more efficient way to run your algorithm,” said Neyenhuis. “There are lots of different circuits you would want to run where this arbitrary angle gate gives you a fairly significant increase in the fidelity of your overall circuit.  This capability also allows for a speed up in the circuit execution by removing unneeded gates, which ultimately reduces the time of executing a job on our machines.”

“This just gave us a big win in fidelity because we can run the sort of interaction you’re after natively, rather than constructing it out of some other Lego blocks.”

Quantinuum has also achieved another milestone with over 500,000 downloads of its TKET open source software development kit.

TKET supports writing and running programs on gate-based quantum computers, allowing developers to optimize quantum algorithms and reduce the computational resources required. It also supports arbitrary angle two-qubit gates.

TKET is open source and accessible through the PyTKET Python package. The SDK also integrates with major quantum software platforms including Qiskit, Cirq and Q#.

This universal availability and TKET’s portability across many quantum processors are critical for building a community of developers who can write quantum algorithms.

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