Researchers “Hide” Ions to Reduce Quantum Errors
A new technique developed by Honeywell researchers reduced the amount of measured “crosstalk” errors by an order of magnitude
Cambridge Researchers at Honeywell Quantum Solutions have turned problematic micromotion that jostles trapped ion qubits out of position into a plus.
The team recently demonstrated a technique that uses micromotion to shield nearby ions from stray photons released during mid-circuit measurement, a procedure in which lasers are used to check the quantum state of certain qubits and then reset them.
Mid-circuit measurement is a key capability in today’s early-stage quantum computers. Because the qubit’s state can be checked and then re-used, researchers can run more complex algorithms – such as the holoQUADS algorithm – with fewer qubits.
By “hiding” ions behind micromotion, Honeywell researchers significantly reduced the amount of “crosstalk” – errors caused by photons hitting neighboring qubits – that occurred when measuring qubits during an operation. (Details are available in a pre-print publication available on the arXiv.)
“We were able to reduce crosstalk by an order of magnitude,” said Dr. John Gaebler, Chief Scientist of Commercial Products at Honeywell Quantum Solutions, and lead author of the paper. “It is a significant reduction in crosstalk errors. Much more so than other methods we’ve used.”
The new technique represents another step toward reducing errors that occur in today’s trapped-ion quantum computers, which is necessary if the technology is to solve problems too complex for classical systems.
“For quantum computers to scale, we need to reduce errors throughout the system,” said Tony Uttley, President of Honeywell Quantum Solutions. “The new technique the Honeywell team developed will help us get there.”
Eliminating errors
Today’s quantum computing technologies are still in the early stage and are prone to “noise” - or interference - caused by qubits interacting with their environment and one another.
This noise causes errors to accumulate, corrupts information stored in and between physical qubits, and disrupts the quantum state in which qubits must exist to run calculations. (Scientists call this decoherence.)
Researchers are trying to eliminate or suppress as many of these errors as possible while also creating logical qubits, a collection of entangled physical qubits on which quantum information is distributed, stored, and protected.
By creating logical qubits, scientists can apply mathematical codes to detect and correct errors and eliminate noise as calculations are running. This multi-step process is known as quantum error correction (QEC). Honeywell researchers recently demonstrated they can detect and correct errors in real-time by applying multiple rounds of full cycles of quantum error correction.
Logical qubits and QEC are important elements to improving the accuracy and precision of quantum computers. But, Gaebler said, those methods are not enough on their own.
“Everything has to be working at a certain level before QEC can take you the rest of the way,” he said. “The more we can suppress or eliminate errors in the overall system, the more effective QEC will be and the fewer qubits we need to run complex calculations.”
Cutting out crosstalk
In classical computing, bit flip errors occur when a binary digit, or bit, inadvertently switches from a zero to one or vice versa. Quantum computers experience a similar bit flip error as well as phase flip errors. Both errors cause qubits to lose their quantum state – or to decohere. In trapped ion quantum computing, one source of errors comes from the lasers used to implement gate operations and qubit measurements.
Though these lasers are highly controlled, unruly photons (small packets of light) still escape and bounce into neighboring ions causing “crosstalk” and decoherence.
Researchers use a variety of methods to protect these ions from crosstalk, especially during mid-circuit measurement where only a single qubit or a small subset of qubits is meant to be measured. With its quantum charged-coupled device (QCCD) architecture, the Honeywell team takes the approach of moving neighboring ions away from the qubit being fluoresced by a laser. But there is limited space along the device, which becomes even more compact as more qubits are added.
“Even when we move them more than 100 microns away, we still get more crosstalk than we prefer,” said Dr. Charlie Baldwin, a senior advanced physicist and co-author of the paper. “There is still some scattered light from the detection laser.”
The team hit on hiding neighboring ions from stray photons using micromotion potentials, which are caused by the oscillating electric fields used to “trap” these charged atoms. Micromotion is typically thought of as a nuisance with ion trapping, causing the ions to rapidly oscillate back and forth, and occurs when the ions are pushed out of the center of the trap by additional electric fields.
“Usually, we are trying to eliminate micromotion but in this case, we were able to use it to our benefit,” said Dr. Patty Lee, chief scientist at Honeywell Quantum Solutions.
The team’s goal is to reduce by 10 million the probability of a neighboring ion absorbing photons at 110 microns away. By moving neighboring ions and hiding them behind micromotion the Honeywell team is approaching that mark.
How and why the technique works
In their paper, Honeywell researchers delved into how and why hiding ions with micromotion works, including the ideal frequency of the oscillations. They also identified and characterized errors. (The basic physics behind the concept of hiding ions was first explored by the ion storage group at the National Institute of Standards and Technology.)
“Mid-circuit operations are a new feature in commercial quantum computing hardware, so we had to invent a new way to validate that the micromotion hiding technique was achieving the low level of crosstalk errors that we predicted,” said Dr. Charlie Baldwin.
Though the new method resulted in a significant reduction of crosstalk errors, the Honeywell team acknowledged there is further to go.
“Crosstalk is one of those scary errors for scaling,” Gaebler said. “It has to be controlled because it becomes more of a problem as you scale and add qubits. This is another tool that will help us scale and help us compact our systems and pack in as many qubits as we can.”
About Quantinuum
Quantinuum, the world’s largest integrated quantum company, pioneers powerful quantum computers and advanced software solutions. Quantinuum’s technology drives breakthroughs in materials discovery, cybersecurity, and next-gen quantum AI. With over 500 employees, including 370+ scientists and engineers, Quantinuum leads the quantum computing revolution across continents.
Visit Quantinuum at SC26 – Booth 4838
Quantinuum is heading to SC26 in Chicago, and we'd love to see you at Booth 4838 in the Quantum Junction. Stop by during exhibit hours to catch partner theater sessions throughout the day, see what's new with Helios and Nexus, and talk with our team about how quantum computing is expanding its footprint in the HPC datacenter, including hybrid quantum-classical applications.
In our booth:
Join our experts and partners at our kiosks and for short sessions in our theater running throughout the day. Topics include:
- Next Gen Enterprise Computing Partners – how leading enterprises are bringing quantum into their computing strategy
- Error Correction: The Path to Fault Tolerance – where quantum error correction stands today and what comes next
- Develop for the Fault Tolerant Era with Nexus – building, running, and managing quantum workflows on the Nexus platfor
- Helios: The Most Accurate Quantum Computer – a closer look at our latest system and what its performance makes possible
- Startup Partners: Accelerating Quantum Ecosystem Innovation – how startups are building on Quantinuum technology
- Real Commercial Impact – quantum applications in pharma, chemicals, materials, and finance
Coffee and cookies on us
Need a break from the show floor? Our barista will be serving up coffee, and we'll have fresh cookies every afternoon. Grab a cup, pull up a seat for a theater session, and chat with the team.
Catch Quantinuum in the SC26 program
Our experts are also speaking in the SC26 technical program. Add these sessions to your schedule (all times CST):
Speaking Sessions
November 15th
9:45 – 10:00am | Room: W178a
Quantum-HPC Workflows Across Multiple Quantum Computing Platforms: Two Case Studies – part of the 2nd International Workshop for Software Frameworks and Workload Management on Quantum-HPC Ecosystems
Presenting: Philipp Seitz
November 16th
3:30 – 4:00pm | Room: W179a
Software for Large Scale Application – part of the 2nd Annual Workshop on Large-Scale Quantum-Classical Computing (LSQCC)
Presenting: Juan Pederson
November 19th
3:30 – 4:00pm | Room: W181abc
Bringing Quantum Computing to the HPC Datacenter
Presenting: Kentaro Yamamoto
See you in Chicago
Whether you're exploring quantum for the first time or planning how to integrate it with your HPC environment, our team is ready to talk. Find us at Booth 4838 in the Quantum Junction, November 16–19.
Fault-tolerant quantum computing is entering a new phase. At Quantinuum, we have demonstrated almost every piece needed for large-scale fault tolerant hardware, from a universal fault tolerant gate set, to a proven fault tolerant architecture, to large-scale materials simulations with encoded qubits, at world-leading fidelity.
However, that’s only half the battle. Developers need practical tools that make this technology accessible without needing to become experts in quantum error correction.
A good quantum computing software stack should capture and reuse QEC1 expertise, turning the complexity of fault tolerance into capabilities that developers can build with.
"Our ambition is for Nexus to be the platform developers turn to for the fault-tolerant era." - Dr. Rajeeb Hazra, President & CEO, Quantinuum
Here at Quantinuum, we are working hard to make that a reality. Since its launch in 2024, Nexus has grown from managing cloud-based quantum workflows into an environment for end-to-end application development and deployment. Our new multi-year roadmap builds on that foundation, connecting software capabilities with each generation of Quantinuum hardware through Apollo, our universal, fault-tolerant quantum computer planned for 2029. Nexus will progressively handle more of the complexity of fault-tolerant development, helping developers build applications that grow in capability as the hardware advances.
With Nexus, you can explore quantum chemistry and materials using InQuanto, and you can make it fault tolerant using our pre-built fault tolerant primitives. You can use GPUs to decode errors in real time, while benefitting from hardware enabled error suppression like Leakage Repump or Dynamical Decoupling. You can also connect your HPC to our QPUs and use Nexus’ Hybrid workflow management system to enjoy the best of both worlds seamlessly.
Of course, all of the above needs a language framework that is fault tolerant in the first place. That’s why we are thrilled to introduce Guppy FT – Nexus’ fault tolerant quantum programming framework, and Guppy Algorithms, Nexus’ library of reusable algorithmic primitives.
Developing for the fault tolerant era: Guppy FT
“The field of QEC is quite abstract, and it is hard for non-experts to gauge what is feasible on current devices. Guppy FT promotes a game-changing paradigm: QEC is no longer just theory, it is also engineering, it is something you can use.” - the Guppy FT team
As we have been saying, the NISQ2 era is coming to an end. The next challenge is to turn fault tolerance from a hardware milestone into a capability developers can use.
We have built the physical QEC architecture: high-fidelity physical qubits, distance scaling and low logical error rates, all-to-all connectivity and reconfigurable qubits, all the primitives working harmoniously, real-time decoding, circuit optimization, and so on. The next step is ensuring our users can easily enjoy the above: with a fault tolerant programming language framework (Guppy FT) inside a fault tolerant user platform (Nexus).
Guppy FT brings three complementary capabilities together:
- A framework for QEC experts to define fault-tolerant architectures.
- Automatic compilation that takes programs written in standard Guppy and turns them into programs running on fault-tolerant architectures.
- Proprietary codes from our own QEC experts that get you the best performance out of our world-leading hardware.
The result is a programming experience in which developers can write quantum algorithms without having to understand the details of the underlying error-correction architecture, while QEC experts retain the ability to define and optimize the architectures that power those programs.
This separation between what the program does and how it is made fault tolerant is central to the approach.
With Guppy FT, QEC experts define the fault-tolerant architecture once, and application developers can program on it without needing to become QEC experts themselves. Developers can continue to write programs in standard, QEC-agnostic Guppy. The Guppy FT framework then automatically lowers those programs into an encoded, fault-tolerant form suitable for execution.
As fault-tolerant techniques improve, the same high-level programming model can therefore serve as a stable interface between applications and increasingly sophisticated QEC implementations. This approach also makes it possible to evolve the underlying architecture without requiring every application developer to rewrite their programs around its implementation details – a crucial benefit as we stay at the forefront of a quickly evolving field.
Available to users today, Guppy FT is an important step toward software designed for the fault-tolerant era. You can use already-perfected codes, like our high-rate quantum error detection code, through Nexus, with more codes coming online as they are developed.
Optimize your work with Guppy Algorithms & Realtime Analytics
We want you doing more than just writing fault tolerant programs – we want to help you write quickly and optimally.
With Guppy Algorithms, you can save needless repetition of work by constructing complex application-level software workflows in an application-agnostic way. Built on Guppy, Guppy Algorithms combines type-safe Guppy primitives with Python builders to help developers construct quantum algorithms out of already optimized building blocks. Guppy Algorithms is also QEC agnostic, enabling users to evolve their fault tolerance approach as the platform grows, without needing to re-write finished programs.
Current highlights include primitives that help you with:
- Trotterisation for Hamiltonian Simulation
- Quantum linear algebra
- Quantum arithmetic
Using Guppy Algorithms is simple. First, you build your abstract (application-specific) algorithm. Then, you simply compose it with Guppy Algorithms: import your desired implementations of circuit sub-components and bring your workflow to life.
"Guppy FT and Guppy Algorithms add a necessary abstraction on top of Guppy’s flexible programming model, so that application development and QEC research can advance in lockstep without either having to bake in assumptions about the other.” - Seyon Sivarajah, Chief Architect of Developer Tools
Soon, we plan to expand Guppy Algorithms to include end-to-end workflows of reusable components.
Of course, a set of optimized building blocks isn’t enough to ensure every program you write is optimal for execution. To that end, Nexus is introducing two tools to help users understand and optimize hardware execution:
- Real-time metrics that provide execution statistics, including gate counts and shot duration.
- ShotPlot, our tool for visualizing gate scheduling, helping users identify idle periods and improve circuit layout.
With these functionalities, you can try new approaches to minimizing gate counts or runtime with real-time feedback that helps you further optimize your result. Taken together, these new tools ensure that Nexus provides an optimal programming experience, from the circuit level to the user experience.
Using Guppy FT to reduce errors on quantum hardware: an end-to-end demonstration on Helios
To demonstrate Guppy FT, the team ran a Steane-encoded quantum algorithm, HHL, on Quantinuum’s Helios quantum computer.
The team compared three versions of the HHL program, with different settings for Guppy FT’s Steane code ([[7, 1, 3]]) encoding, each with 500 shots. The first used no explicit QEC cycles and performed on-demand, sequential state preparation. The second used Guppy FT’s state factories to parallelize state preparation, and the third also applied three QEC cycles to each of the five qubits.
Each shot is comprised of three stages: the HHL program, mid-circuit error detection, and the inverse of the HHL program. Mid-circuit error detection measures the ancilla qubits used by the HHL program, which it ought to disentangle from the data qubits. If an error is detected, the shot is discarded; otherwise, it moves on to the final stage and is marked as accepted. Fidelity is computed as the proportion of accepted shots that the inverse HHL program successfully returns to the initial state.
The results show that both QEC cycles and parallelized state preparation improve performance. QEC cycles actively correct errors while parallelization shortens execution time, reducing the chance of errors. Together, these results demonstrate how Guppy FT can implement fault-tolerant architectures for practical, end-to-end programs running on real quantum hardware.
Deploy Your Hybrid Quantum-Classical Application
The future of quantum computing is more than fault tolerant: it’s hybrid. Close co-ordination between classical and quantum computing resources will be essential for most killer use-cases, with a combination of AI, HPC, and QPU each working on the sub-components they are best suited for.
We’ve been perfecting hybridization for years now, including hybridizing our QPUs with the Fugaku supercomputer at RIKEN. Along the way, we have developed a robust event-based hybrid compute runtime, now available through Nexus. Our updated hybrid compute framework features:
- Multiple storage implementations
- Workflow attempts and restart improvements
- Runtime configuration files
- OTEL tracing and observability
- Workflow cancellation
- SQLite based state management
Quantinuum Nexus: A foundation for what comes next
Nexus brings together the capabilities and infrastructure needed to develop, analyze, run, and manage hybrid quantum-classical programs across the stack. By unifying quantum programming, validation, fault tolerance, compilation, and execution in one place, with interoperability across third-party environments, Nexus is making fault tolerance a practical reality.
Nexus users are already using our quantum processors to explore applications in finance, nuclear physics, particle physics, benchmarking, computational chemistry, and more. As our Nexus roadmap evolves, we plan on deploying ecosystem tools and libraries, as well as an applications marketplace where developers can monetize their work.
“Quantum computers are on the brink of achieving fault tolerance at scale. It's exciting: we are entering terra incognita for what we can compute. The new challenge is putting our high-level quantum algorithms into the right form to successfully run on error-corrected hardware. Developer platforms like Nexus help us bridge that gap between quantum algorithm design and deployment
-José Ignacio Latorre, Director, Centre for Quantum Technologies at the National University of Singapore at the National University of Singapore
By bringing everything together, Nexus is becoming a robust platform in which fault tolerance is a feature, rather than a barrier to entry.
Get ready for the fault tolerant future.
1 Quantum Error Correction
2 Noisy Intermediate Scale Quantum
By Chris Langer
Trustworthy answers are a prerequisite for useful quantum computing. First build machines that deliver answers reliably. Then focus on delivering them quickly.
A trustworthy answer also needs to arrive soon enough to be useful. But understanding how long that takes requires looking beyond the speed of any single operation.
Think about your commute: a car’s 0–60 time doesn’t tell you when you’ll arrive. Traffic, detours, and bottlenecks all affect the journey. Quantum computing works much the same way. No isolated metric, including gate speed, indicates how quickly the entire system can get the job done.
The goal of quantum computing is to solve valuable problems reliably and soon enough to matter.
At Quantinuum, we are pursuing that goal by scaling our systems and removing bottlenecks. Speed depends on how much work is required to make a computation reliable and how much of that work can happen simultaneously. We are improving how we build and operate logical qubits—an essential mechanism for complex computations—through more efficient error correction, faster qubit movement, and more parallel operations.
Understanding how these advances translate into faster answers starts with looking beyond the speed of a single gate.
The Gap Between Fast Gates and Useful Answers
Gate speed reveals how quickly a single step happens in a quantum calculation. It does not tell us how many steps are needed, how many can happen together, or how often a computation must be repeated.
An example illustrates the distinction.
Researchers from the University of Tokyo ran a small, three-qubit circuit on superconducting and trapped-ion systems.1 Armed with faster gates, the superconducting machine executed the circuit roughly 200 times faster. But it needed about 50 times more repetitions to reach comparable accuracy, reducing its practical speed advantage to approximately four times.
Faster gates led to faster answers in this example, but the headline execution speed overstated the advantage dramatically.
Even on a modestly larger circuit, the fourfold advantage could disappear entirely. A more complicated circuit means more room for errors and significantly more repetitions to overcome them. Now consider what is required of the systems, larger still, to solve real-world challenges. This calls for a move to logical qubits, which spread information across multiple physical qubits so that errors can be detected and corrected without loss.
At that scale, the question becomes how quickly the system can do useful work while keeping errors under control. The metric that tracks the rate of useful work is logical throughput, the amount of useful work a system completes per second.
What Drives Logical Throughput and Faster Answers
Logical throughput depends on logical clock rate (how quickly logical operations happen) and parallelism (how many can happen at once).
Consider two hypothetical machines: the first completes one logical operation at a time, each taking a microsecond. The second performs 1,000 independent logical operations simultaneously, each taking a millisecond. In one millisecond, each machine completes 1,000 operations. The second machine’s operations take 1,000 times longer, but parallelism offsets the difference.
Error correction takes time and physical qubits. Using both more efficiently can speed up logical operations and enable more work in parallel.
Three levers help improve that throughput:
Connectivity. Better connectivity enables error correction that is more efficient in time and space. Faster correction improves logical clock rate; fewer physical qubits per logical qubit leave room for more logical qubits. Connectivity also enables logical operations to work in parallel.
Fidelity. More reliable physical operations reduce the resources needed for error correction. This improves efficiency in space: fewer physical qubits can deliver the required logical reliability, leaving capacity for more logical qubits.
Scale. More physical qubits create room for more logical qubits. Efficient error correction, strong connectivity, and enough places to perform operations help turn that added capacity into more work happening at once. As systems scale to 1,000 logical qubits and beyond, putting more qubits to work simultaneously can help offset slower individual operations.
How Quantinuum Is Turning Scale into Speed
Faster gates, better connectivity, efficient error correction, and greater parallelism must work together. That is the thinking behind Quantinuum’s approach to scaling.
We are working to accelerate gate execution, qubit movement, and other factors while reducing unnecessary operations and improving error-correction efficiency. More efficient error correction lets us reach the required reliability with fewer resources. That means we can exploit parallelism and spend more of our extra qubits on speed.
Superconducting systems, by contrast, boast faster clock speeds, but limited connectivity forces more operations to run in sequence. That constrains the parallel capabilities of these systems, the other side of the throughput equation. Put simply, completing each step faster does not guarantee finishing the job sooner if more steps must wait their turn. Greater error-correction overhead also leaves fewer logical qubits available for computation from a given number of physical qubits. Even with more logical qubits, connectivity remains a separate constraint on how many operations can run in parallel. Together, these factors limit how effectively faster physical gates translate into faster computation.
Quantinuum’s architecture allows us to scale logical qubits and facilitate greater throughput. Maximizing the value of qubits remains an engineering challenge, which our roadmap to larger, faster machines addresses in three steps:
First, improve how qubits move. Sol, planned to launch in 2027, is our expected proving ground for a two-dimensional architecture that allows more efficient, parallel rearrangement of qubits as the system grows. Our prototypes have already demonstrated our two-dimensional geometry, operating concepts, and scalable controls work.2 We continue to improve the speed of qubit movement.
Second, create more places to work simultaneously. Adding operating zones enables more operations to run at once, increasing throughput by leveraging space.
Third, increase scale. Our planned progression from Sol to Apollo (targeted to launch in 2029) and then Lumos in the decade ahead is intended to increase physical qubit counts from approximately 200 to thousands and eventually millions.
On these larger systems, efficient error correction and connectivity-enabled parallelism will allow us to turn more qubits into dramatically higher computational throughput.
Measure the Time to a Useful Answer
As quantum computers grow, they must solve larger problems in a useful amount of time. Fast gates can’t guarantee that. Any speed advantage on a small, uncorrected circuit could vanish at the logical level. For superconducting systems, scaling this small-scale edge would mean overcoming architectural limits on connectivity and efficient error correction, which is no small feat.
For users and investors, the speed equation includes how much work the system requires, how efficiently it corrects errors, and how much computation it can perform at once. Additional qubits deliver their full value when these capabilities translate scale into increased logical throughput.
It doesn’t matter how fast you get to the wrong answer. What matters is getting the right answers efficiently. Returning to the commute analogy, we’re adding horsepower to our car and identifying the traffic detours on the road. The measure of progress will be how quickly we arrive at the destination.
References:
[1] E. Lötstedt and K. Yamanouchi, “Comparison of current quantum devices for quantum computing of Heisenberg spin chain dynamics,” Chemical Physics Letters, vol. 856, Art. no. 141817, Feb. 2024, doi: 10.1016/j.cplett.2023.141817.
[2] R. D. Delaney et al., “Scalable Multispecies Ion Transport in a Grid-Based Surface-Electrode Trap,” Physical Review X, vol. 14, no. 4, p. 041028, 2024, doi: 10.1103/PhysRevX.14.041028.
Forward-Looking Statements
This post contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These include statements about Quantinuum's technology and product roadmap; the expected timing, capabilities, and performance of future systems, including Sol, Apollo, and Lumos; anticipated improvements in error correction, qubit transport, parallelism, and logical throughput; and the potential applications of quantum computing. Words such as "will," "intend," "plan," "expect," "target," "designed to," "may," "can," "could," and similar expressions identify forward-looking statements.
These statements are based on current expectations and assumptions and are subject to risks and uncertainties that could cause actual results to differ materially. These risks include technical challenges in scaling quantum hardware and error correction; delays in development, manufacturing, or supply of components; the pace of customer adoption; competition and advances in alternative technologies; our ability to fund research and development; and the other risks described under "Risk Factors" in the prospectus for our initial public offering and in our most recent Quarterly Report on Form 10-Q, each filed with the Securities and Exchange Commission. Forward-looking statements speak only as of the date of this post, and we undertake no obligation to update them, except as required by law.