On the heels of two major quantum computing achievements last month, Tony Uttley, President and COO of Quantinuum, made three more announcements at IEEE Quantum Week 2022. The company’s latest announcements include another quantum volume record, a new method to make two-qubit gates with higher fidelity and greater efficiency, and a milestone achievement of more than a half-million downloads of Quantinuum’s open-source software development kit (SDK) called TKET.
Before analyzing the latest announcements, it's important to review Quantinuum’s quantum hardware and architecture that made those announcements possible.
Quantum Charged Coupled Device
There are two common ion traps, linear traps and quantum charged-coupled device (QCCD). The linear trap is exactly what it sounds like – a long chain of ion qubits contained in a single trapping zone. Linear traps have some shortcomings such as the limited ability to scale qubits in large numbers; it also has some limitations with qubit addressability. QCCD has its limitations as well, but nearly all major problems have been solved.
In July, Quantinuum solved a technical QCCD problem that has baffled the quantum research community for years when its scientists developed a method to allow ions to make 90-degree turns when moving through ion trap intersections. This is covered in more detail later.
QCCD was first proposed in a research paper by Dr. David Wineland and his NIST group over twenty years ago. However, Quantinuum was the first company to implement and improve it. Dr. Chris Monroe, co-founder and Chief Scientist for IonQ, also Professor of Physics and ECE at Duke University, was one of the authors of that paper.
Rather than storing and performing qubit operations in a single linear trapping zone, QCCD uses multiple zones for the arbitrary rearrangement of qubits and accommodation of various codes, including those with exotic geometries. Small chains of ions in multiple small zones provides greater precision and control compared to large ion chains within a single trapping zone.
Of the two architectures, QCCD is considered the most advanced and most flexible. Quantinuum’s H-Series quantum computer currently has 20 qubits spread across 5 gating zones where qubits are parked, and quantum operations are performed. Ions can be moved from one zone to the next and then recombined. The architecture provides high-fidelity interactions between distant qubits and low crosstalk between gates. All of Quantinuum’s recent advancements have been made possible by QCCD’s high fidelity and flexibility.
Tony Uttley is confident that QCCD will support Quantinuum’s quantum roadmap of future generations of H-Series processors. He feels that QCCD offers a superior menu of technical advantages and provides greater adaptability not only for technical reasons, but for future market needs as well.
While QCCD qubit control is precise, qubit control in a single linear trapping zone with 50 or more qubits can be problematic. Packing many ions together in single traps can adversely affect spacing between ions which makes it difficult to address individual ionsand create unwanted interactions between them. Fiber optics and optical switches may allow interconnection of multiple linear traps in the future, allowing for greater control and scaling. However, there are no optical switches available today that are fast enough to stitch a multi-chip trapped-ion architecture together.
Dr. Jungsang Kim is Co-founder and Chief Technology Officer of IonQ. He is also Professor of Physics in the Department of Electrical and Computer Engineering at Duke University. While working for Bell Labs in the early 2000s, Dr. Kim built the world's largest optical switch with over a thousand ports. Dr. Kim is currently working on an optical switch for IonQ's future architecture.
Quantinuum announcements at IEEE Quantum Week
- Arbitrary angle entangling gate capabilities: Single qubit gates and fully entangling two-qubit gates are routinely used to build quantum circuit operations. Because there are a lot of algorithms that don’t need fully entangling two-qubit gates, Quantinuum developed a method using arbitrary angle partially entangling gate that increases efficiency and reduces errors. Lower errors allow more complex problems to be run.
Dr. Brian Neyenhuis is the Director of Commercial Operations at Quantinuum. When asked if the method was proprietary, Dr. Neyenhuis explained that the technique was not proprietary to Quantinuum.
“Other companies may be able to implement arbitrary angle entangling gates at some point in the future,” he said. “However, we have an advantage with QCCD because when we do a two qubit gate, it's only those two specific qubits in the interaction zone with laser beams. That makes it very straight forward. If there are too many qubits, such as in a linear trap, you have to worry about crosstalk which occurs when many qubits interacting together; and you also have to be careful about what the other qubits are doing. You can do those things with longer chains but it’s a lot harder.”
Dr. Neyenhuis also pointed out there are algorithms where the arbitrary angle two-qubit gate act as a natural building block. In general, the arbitrary angle gate can run on many quantum circuit types. He gave the quantum Fourier Transform as an example.
The Fourier Transform has been called one of the most useful mathematical tools in modern science and engineering. Dr. Neyenhuis explained that use of arbitrary angle two-qubit gates in the quantum Fourier Transform can reduce the number of two-qubit gates needed for the transform by 2x, plus it can reduce overall errors by 2x as well. Greater circuit fidelity offers the advantage of running deeper and more complex circuits. More information about arbitrary angle entangling gates can be found here
- Record quantum volume 8192 attained by using arbitrary angle entangling gates: Setting Quantum Volume (QV) records is nothing new for Quantinuum (or previously as Honeywell Quantum Solutions). However, there is something new about this record - Quantinuum used its new arbitrary angle partially entangling gate to help achieve it’s newest record quantum volume. The new QV record of 8192 (213) is double Quantinuum’s previous volume record of 4096 set only five months ago. In fact, it is the seventh time in two years that Quantinuum’s H-Series system has set the record for a measured QV. Quantinuum’s goal is to increase quantum volume by 10X annually.
IBM originally developed quantum volume in 2017 as a hardware-agnostic performance measurement for gate-based quantum computers such as the Quantinuum H-Series system. QV testing measures many aspects of a quantum computer. Although the number of qubits is important, there are also other system factors that affect a quantum computer’s performance such as qubit connectivity, gate fidelity, cross talk, circuit compiler efficiency, and more. A high quantum volume is an indicator of a quantum computer’s power.
QV score is determined by running specified algorithms and arbitrary circuits. For this QV record, Quantinuum ran 220 quantum volume circuits 90 times each.
Quantinuum scientists found that arbitrary angle two-qubit gates performed more efficiently and with less errors at each step of the algorithm. The cumulative effect of the arbitrary angle gates helped boost quantum volume to its current record value of 8192.
Quantinuum plans to continue the use of quantum volume until a better metric is created and endorsed by the ecosystem. More complete information about the new quantum volume record can be found here.
- A big number for TKET downloads
Tony Uttley also announced that Quantinuum achieved a milestone of surpassing 500,000 downloads of TKET.
TKET is Quantinuum’s open source SDK used by developers writing quantum algorithms for gate-based quantum computers. It is universally accessible through the PyTKET Python package. Functionally, it optimizes quantum algorithms by reducing computational resources. The TKET SDK also integrates with Qiskit, Cirq and Q#.
Since the software is downloaded both by companies and academic institutions with multiple users, the user count is likely greater than 500,000. Quantinuum estimates that the TKET base is growing globally and now has close to a million users.
Quantinuum plans to continually evolve the TKET platform as updates and advancements occur to ensure it includes new hardware capabilities such as Quantinuum’s most recent development, arbitrary angle two-qubit gates.
Over the past 12 months, Quantinuum scientists have performed a great deal of research. However, there are two previous pieces of standout research that should be highlighted:
- Highlighted research #1 - Shuttling ion pairs through intersections and negotiating 90 degree turns: In July, Quantinuum researchers discovered how to move two ions of different species - ytterbium and barium - simultaneously through an intersection of a microfabricated prototype trap with a grid-like structure. The research demonstrated that an ion pair could turn 90 degree corners with speed but without excessive motion.
It may not sound significant, but this research provides the capability to execute Quantinuum’s long term roadmap for future generations of H-series quantum computers. Quantinuum is following the pre-merger hardware strategy originally developed by Honeywell Quantum Solutions. That plan calls for the System Model H-2 to use a racetrack-like design shown in the above graphic. H-Series System Model H-3, H-4, and H-5 will use two-dimensional traps that resemble a city street grid with multiple railroad lines and intersections.
Limitations inherent in the QCCD grid design are what motivated Quantinuum scientists to pursue research needed to move ion pairs through grid intersections together and make sharp corner turns without excessive energy and motion.
Ion trap researchers have been working on this problem for years. Prior to Quantinuum’s research, it was believed that the only way for paired ions to move through zones was to first separate the pair, then move them through junctions one at a time. That solution would have significantly increased processing time.
2. Highlighted research #2 - Closing the gap on fault-tolerant quantum error correction: Fault tolerant quantum error correction will make it possible to build quantum computers with enough qubits to solve problems far beyond the computational reach of today’s largest and most powerful supercomputers.
Qubits are very sensitive to sources of noise in their environment which can result in random errors during quantum computation. Uncorrected errors can accumulate to the point that viable computation isn’t possible. It is currently not possible to build quantum computers with millions of qubits due to the lack of quantum error correction (QEC).
QEC is both a physics and engineering problem. In the quantum ecosystem, nearly every academic and commercial institution is performing some level of QEC research. The entire ecosystem has invested years of research into QEC and yet a complete fault tolerant QEC solution has yet to be developed, which illustrates its complexity and difficulty. Even so, much progress has been made.
A good example is the research paper Quantinuum published in August that illustrates two important error correction firsts.
These “firsts” were made possible by using physical qubits to form logical qubits. Each logical qubit is formed from groups of entangled physical qubits that perform computations while other qubits are tasked with error detection and correction.
Several years ago, it was thought that 1000 physical qubits would be needed for each logical qubit. Now that ratio is down to 10 to 1 or less.
For the first time, Quantinuum researchers were able to construct a logical entangling circuit that had a higher fidelity than its physical counterpart. The researchers also accomplished another QEC first by entangling two logical qubit gates in a fully fault-tolerant manner using real-time QEC.
Key to this demonstration is its repeatability, a necessity for any QEC solution. While the research does not provide a complete QEC solution, it is stil an important proof of concept that creates a new starting point for other researchers to build on.
More information on Quantinuum error correction research can be found here.
3. Quantinuum research performed over the past 12 months:
September 27, 2022
Quantinuum Sets New Record with Highest Ever Quantum Volume of 8192
August 4, 2022
Logical qubits start outperforming physical qubits
July 11, 2022
Quantum Milestone: Turning a Corner with Trapped Ions
June 14, 2022
Quantinuum Completes Hardware Upgrade; Achieves 20 Fully Connected Qubits
May 24, 2022
Quantinuum Introduces InQuantoTM to Explore Industrially Relevant Chemistry Problems on Today’s Quantum Computers
April 14, 2022
Quantinuum Announces Record Quantum Volume of 4096
March 29, 2022
On the ArXiv: Modeling Carbon Capture with Quantum Computing
March 29, 2022
Quantinuum Announces Updates to Quantum Natural Language Processing Toolkit λambeq, Enhancing Accessibility
March 3, 2022 Quantinuum announces a world record in fidelity for quantum computing qubits
December 29, 2021 Demonstrating Benefits of Quantum Upgradable Design Strategy: System Model H1-2 First to Prove 2,048 Quantum Volume
December 7, 2021
Introducing Quantum Origin, The world’s first quantum-enhanced cryptographic key generation platform to protect data from cybersecurity threats
(Note: On November 30, 2021, Quantinuum was formed by the merger beteen Honeywell Quantum Solutions and Cambridge Quantum)
November 27, 2021
Quantum Milestone: We Can Now Detect and Correct Quantum Errors in Real Time
November 29, 2021
LAMBEQ: A Toolkit for Quantum Natural Language Processing
November 29, 2021
How a New Quantum Algorithm Could Help Solve Real-world Problems Sooner
November 29, 2021
Quantum Milestone: 16-Fold Increase in Performance in a Year
October 15, 2021
Researchers ‘Hide’ Ions to Reduce Quantum Errors By Reducing Crosstalk Errors An Order of Magnitude
October 20, 2021
TKET: Quantum Software Tool Goes Open Source
Note: Moor Insights & Strategy writers and editors may have contributed to this article.