#Fault Tolerant Quantum Computing

[tez-world1]

Here are a few title options optimized for Tumblr, incorporating keywords and designed to be catchy: **Option 1 (Shorter, punchier):** Quantum Computing's HUGE Leap! 🚀 Error-Free Future? **Option 2 (More descriptive):** Quantum Computing Breakthrough! Error Correction Solved? 🤯 **Option 3 (Question format, engaging):** Is Quantum Computing's Error Problem FINALLY Solved?! 🚀 **Option 4 (Benefit-driven):** Faster Drugs, Unbreakable Codes? Quantum Computing's Giant Leap! **Tips for Tumblr:** * **Emojis:** Use relevant emojis to grab attention in the Tumblr feed. * **Keep it concise:** Tumblr users often scan titles quickly. * **Create intrigue:** Use words like "solved," "breakthrough," and "finally" to generate excitement. * **Keywords:** Include important keywords like "quantum computing," "breakthrough," and "error correction." Remember to also use the hashtags you provided in your Tumblr post. The URL is already included in your text, so no need to add that to the title itself.

Quantum Computing Just Leapt a HUGE Hurdle! 🚀 For years, errors plagued quantum computing. But a groundbreaking new discovery might change EVERYTHING! Scientists have finally overcome a major obstacle, bringing us closer to fault-tolerant quantum computers. This means faster drug discovery, revolutionary materials, and even unbreakable encryption could be on the horizon. 🤯 Learn more about this incredible leap forward in our latest blog post: http://tezlinks.blogspot.com/2024/12/quantum-computing-leap-beyond-error.html #quantumcomputing #science #technology #breakthrough #innovation #computerscience #futureoftech ```

[manmishra]

🚀💻 Microsoft Unveils Majorana 1 Quantum Processor! 💡⚛️ A giant leap in Quantum Computing with Topological Qubits! 🌌🧠 ✅ Faster Processing ⚡ ✅ Fewer Errors 🛡️ ✅ Scalable Quantum Power 💽 This could revolutionize AI 🤖, Healthcare 💊, Cybersecurity 🔐, and more! 💯🔥 👉 Are we stepping into a Quantum Future? 🤯🔮 #Microsoft #QuantumComputing #FutureTech #AI #Majorana1 💻⚛️

[jcmarchi]

Microsoft’s Majorana hype: Real proof or just marketing?

New Post has been published on https://thedigitalinsider.com/microsofts-majorana-hype-real-proof-or-just-marketing/

Microsoft’s Majorana hype: Real proof or just marketing?

Introduction: The quest for reliable qubits

Quantum computing faces a fundamental challenge: qubits, the basic units of quantum information, are notoriously fragile.

Conventional approaches, such as superconducting circuits and trapped ions, require intricate error-correction techniques to counteract decoherence. Microsoft has pursued an alternative path: Majorana-based topological qubits, which promise inherent noise resistance due to their non-local encoding of quantum information.

This idea, based on theoretical work from the late 1990s, suggests that quantum states encoded in Majorana zero modes (MZMs) could be immune to local noise, reducing the need for extensive error correction. Microsoft has invested two decades into developing these qubits, culminating in the recent “Majorana 1” prototype.

However, given past controversies and ongoing skepticism, the scientific community remains cautious in interpreting these results.

The scientific basis of Majorana-based qubits

Topological qubits derive their stability from the spatial separation of Majorana zero modes, which exist at the ends of specially engineered nanowires. These modes exhibit non-Abelian statistics, meaning their quantum state changes only through specific topological operations, rather than local perturbations. This property, in theory, makes Majorana qubits highly resistant to noise.

Microsoft’s approach involves constructing “tetrons,” pairs of Majorana zero modes that encode a single logical qubit through their collective parity state. Operations are performed using simple voltage pulses, which avoids the complex analog controls required for traditional superconducting qubits.

Additionally, digital measurement-based quantum computing is employed to correct errors passively. If successful, this design could lead to a scalable, error-resistant quantum architecture.

However, while the theoretical framework for Majorana qubits is robust, experimental verification has been challenging. Majorana zero modes do not occur naturally and must be engineered in materials like indium arsenide nanowires in proximity to superconductors.

Establishing that these states exist and behave as expected has proven difficult, leading to past controversies.

Historical controversies: The 2018 retraction

A major setback for Microsoft’s Majorana initiative occurred in 2018 when researchers, including Leo Kouwenhoven’s team at TU Delft (funded by Microsoft), published a Nature paper claiming to have observed quantized conductance signatures consistent with Majorana zero modes.

This was hailed as a breakthrough in topological quantum computing. However, by 2021, the paper was retracted after inconsistencies were found in data analysis. Independent replication attempts failed to observe the same results, and an internal investigation revealed that a key graph in the original paper had been selectively manipulated.

This event, dubbed the “Majorana Meltdown,” significantly damaged the credibility of Microsoft’s approach. It highlighted the challenge of distinguishing genuine Majorana modes from other quantum states that mimic their signatures due to material imperfections. Many physicists became skeptical, arguing that similar issues could undermine subsequent claims.

Experimental progress and remaining challenges

Despite the 2018 controversy, Microsoft and its collaborators have continued refining their approach. The recent announcement of the “Majorana 1” chip in 2025 presents experimental evidence supporting the feasibility of Majorana-based qubits.

Key advancements include:

Fabrication of “topoconductor” materials: Microsoft developed a new indium arsenide/aluminum heterostructure to reliably host Majorana zero modes.

Parity measurement success: The team demonstrated that they could measure the qubit’s parity (even vs. odd electron occupation) with 99% accuracy, a crucial validation step.

Increased parity lifetime: The qubit’s state exhibited stability over milliseconds, significantly surpassing superconducting qubits’ coherence times (which are typically in the microsecond range).

Digital control implementation: Unlike analog-tuned superconducting qubits, Majorana qubits can be manipulated with simple voltage pulses, theoretically enabling large-scale integration.

While these are important steps forward, the experiments have not yet demonstrated key quantum operations, such as two-qubit entanglement via non-Abelian braiding. Until this milestone is achieved, claims about the superiority of topological qubits remain speculative.

Comparison with other qubit technologies

To assess Microsoft’s claims, it is useful to compare Majorana qubits with existing quantum computing platforms:

Superconducting qubits (IBM, Google): These have demonstrated successful quantum error correction and multi-qubit entanglement but require extensive calibration and error correction. Fidelity levels for two-qubit gates currently range around 99.9%.

Trapped-ion qubits (IonQ, Quantinuum): These offer superior coherence times (seconds vs. microseconds for superconductors) but suffer from slow gate speeds and complex laser-based control.

Majorana-based qubits: Theoretically provide built-in error protection, reducing the need for extensive error correction. However, experimental validation is still in progress, and large-scale integration remains untested.

Microsoft has argued that Majorana qubits will enable a quantum computer with a million qubits on a single chip, a feat that conventional qubits struggle to achieve.

While this is an exciting possibility, many researchers caution that scaling challenges remain, especially given the extreme conditions (millikelvin temperatures, precise nanowire fabrication) required for Majorana qubits.

Despite recent progress, many physicists remain skeptical of Microsoft’s claims.

Key concerns include:

Lack of direct evidence for Majorana zero modes: While Microsoft’s 2025 Nature paper presents strong supporting data, the scientific community has yet to reach a consensus that Majorana modes have been definitively observed.

Alternative explanations for observed phenomena: Many experimental signatures attributed to Majorana states could be explained by disorder-induced states or other trivial effects in semiconductor-superconductor interfaces.

Unverified large-scale claims: Microsoft’s assertion that its approach will lead to fault-tolerant quantum computing “within years, not decades” is met with skepticism. Experts note that even the most advanced conventional quantum computers are still years away from practical applications, and scaling from an 8-qubit chip to a million-qubit processor is an enormous leap.

Comparison to competing approaches: Some argue that improvements in quantum error correction for superconducting and trapped-ion qubits may render topological qubits unnecessary by the time they are fully realized.

A Promising but unproven path

Microsoft’s Majorana-based qubits represent one of the most ambitious efforts in quantum computing. The theoretical promise of intrinsic error protection and simplified quantum control is compelling, and recent experiments provide encouraging evidence that topological qubits can be realized.

However, historical controversies, ongoing skepticism, and the lack of key demonstrations (such as two-qubit gates) mean that these qubits are not yet a proven alternative to existing technologies.

While Microsoft has made significant strides in overcoming past setbacks, their claims of imminent large-scale quantum computing should be met with caution.

The coming years will be critical in determining whether Majorana qubits will revolutionize quantum computing or remain an elegant but impractical idea. As independent verification and further experiments unfold, the scientific community will ultimately decide whether Microsoft’s bold bet pays off.

[materialsscienceandengineering]

Quantum Computing with a Twist

The prediction that twisted semiconductor bilayers can host so-called non-Abelian states without a magnetic field holds promise for fault-tolerant quantum computing. [...] Scientists think that the performance of quantum computers could be improved by using hypothesized phases of matter known as non-Abelian states, which have the potential to encode information in an error-resistant way. But realizing a material that could host such states typically requires a powerful magnetic field, which would hinder device integration. Now three teams have predicted that non-Abelian states can form in certain semiconductor structures without a magnetic field [1–3]. If this prediction is confirmed experimentally, it could lead to more reliable quantum computers that can execute a wider range of tasks.

Read more.

[govindhtech]

Craig Gidney Quantum Leap: Reduced Qubits And More Reliable

A Google researcher reduces the quantum resources needed to hack RSA-2048.

Google Quantum AI researcher Craig Gidney discovered a way to factor 2048-bit RSA numbers, a key component of modern digital security, with far less quantum computer power. His latest research shows that fewer than one million noisy qubits could finish such a task in less than a week, compared to the former estimate of 20 million.

The Quantum Factoring Revolution by Craig Gidney

In 2019, Gidney and Martin Ekerå found that factoring a 2048-bit RSA integer would require a quantum computer with 20 million noisy qubits running for eight hours. The new method allows a runtime of less than a week and reduces qubit demand by 95%. This development is due to several major innovations:

To simplify modular arithmetic and reduce computing, approximate residue arithmetic uses Chevignard, Fouque, and Schrottenloher (2024) techniques.

Yoked Surface Codes: Gidney's 2023 research with Newman, Brooks, and Jones found that holding idle logical qubits maximises qubit utilisation.

Based on Craig Gidney, Shutty, and Jones (2024), this method minimises the resources needed for magic state distillation, a vital stage in quantum calculations.

These advancements improve Gidney's algorithm's efficiency without sacrificing accuracy, reducing Toffoli gate count by almost 100 times.

Cybersecurity Effects

Secure communications including private government conversations and internet banking use RSA-2048 encryption. The fact that quantum-resistant cryptography can be compromised with fewer quantum resources makes switching to such systems more essential.

There are no working quantum computers that can do this technique, but research predicts they may come soon. This possibility highlights the need for proactive cybersecurity infrastructure.

Expert Opinions

Quantum computing experts regard Craig Gidney's contribution as a turning point. We offer a method for factoring RSA-2048 with adjustable quantum resources to bridge theory and practice.

Experts advise not panicking immediately. Quantum technology is insufficient for such complex tasks, and engineering challenges remain. The report reminds cryptographers to speed up quantum-secure method development and adoption.

Improved Fault Tolerance

Craig Gidney's technique is innovative in its tolerance for faults and noise. This new approach can function with more realistic noise levels, unlike earlier models that required extremely low error rates, which quantum technology often cannot provide. This brings theoretical needs closer to what quantum processors could really achieve soon.

More Circuit Width and Depth

Gidney optimised quantum circuit width (qubits used simultaneously) and depth (quantum algorithm steps). The method balances hardware complexity and computing time, improving its scalability for future implementation.

Timeline for Security Transition

This discovery accelerates the inevitable transition to post-quantum cryptography (PQC) but does not threaten present encryption. Quantum computer-resistant PQC standards must be adopted by governments and organisations immediately.

Global Quantum Domination Competition

This development highlights the global quantum technological competition. The US, China, and EU, who invest heavily in quantum R&D, are under increased pressure to keep up with computing and cryptographic security.

In conclusion

Craig Gidney's invention challenges RSA-2048 encryption theory, advancing quantum computing. This study affects the cryptographic security landscape as the quantum era approaches and emphasises the need for quantum-resistant solutions immediately.

[frank-olivier]

Quantum Simulation: A Frontier in Scientific Research

Quantum simulation, a burgeoning field in modern physics, leverages the unique properties of quantum systems to replicate and investigate the behavior of other complex quantum systems. This approach offers a powerful tool to study intricate quantum phenomena that are otherwise challenging to analyze using classical computational methods or experimental setups. By harnessing the principles of quantum mechanics, quantum simulation enables researchers to explore parameter spaces inaccessible to classical simulations and gain unique insights into the underlying physics.

One of the primary platforms for quantum simulation is ultracold atomic gases, cooled to temperatures close to absolute zero. The low temperatures and high phase-space density of these systems allow for the study of individual atoms and molecules in a highly controlled environment, with minimal interactions with the surrounding environment. Optical lattices, created by interfering laser beams, provide a versatile and highly controllable platform for quantum simulations. By adjusting the laser parameters, researchers can engineer various types of lattice structures, enabling the study of phenomena such as Anderson localization, quantum phase transitions, and many-body dynamics. The periodic potential created by the optical lattice can mimic the crystal lattice of solid-state systems, allowing for the investigation of condensed matter physics in a clean and controllable environment.

Superconducting qubits, trapped ions, and nitrogen-vacancy centers in diamonds are alternative platforms for quantum simulation, each with its unique strengths and capabilities. Superconducting qubits use superconducting circuits to encode quantum information and exhibit long coherence times. Trapped ions allow for precise control and readout of their quantum states using electromagnetic fields. Nitrogen-vacancy centers in diamonds offer long-lived spins and coupling to other spins, making them useful for quantum information processing and sensing applications.

A significant challenge in quantum simulation is minimizing and correcting errors, which can arise from imperfections in the experimental setup or external disturbances. These errors can lead to decoherence, causing the quantum system to lose its coherence and become difficult to control. Researchers have developed robust quantum simulation methods and error correction codes to mitigate these errors and extend the capabilities of quantum simulations. Techniques such as quantum error correction, dynamical error suppression, and fault-tolerant quantum computing aim to overcome these challenges and enable longer and more accurate quantum simulations.

Quantum simulation has enabled the discovery of new phases, such as topological insulators and supersolids, and the study of strongly correlated systems, like high-temperature superconductors. By mimicking condensed matter systems in the laboratory, researchers can observe and understand their behavior in detail, leading to a deeper understanding of quantum phenomena and the development of new materials and technologies. Quantum simulations have the potential to revolutionize fields such as condensed matter physics, materials science, and chemistry. By simulating molecular Hamiltonians, quantum simulations can provide insights into chemical reactions, electronic structures, and excited states, with implications for drug discovery and materials design. Furthermore, quantum simulations can accelerate materials discovery by predicting the properties of new materials and optimizing existing ones for specific applications.

Esteban Adrian Martinez: Introduction to Quantum Simulators (Summer School on Collective Behaviour in Quantum Matter, September 2018)

Tuesday, November 5, 2024

[natthedyke]

Quantum computers are like this, primarily, because they're very sensitive, and therefore hang from ceilings to reduce interference from vibrations (This part is me wondering out loud: Fault Tolerance [Basically computers being able to take a certain number of bad bits in their computation] is a thing built into regular computers that quantum computers are only just starting to get, I wonder if they'll be able to have slightly more regular structures as these become better developed.)

Additionally, quantum computers use super conductors ( Materials that can conduct electricity with no resistance) which currently only exist under very high pressure or very low temperatures (Though we did just discovery an ambient pressure superconductor that works at 40 k!) Which is why they need these very weird looking cooling systems.

why did no one tell me quantum computers looked like that

[geeknik]

Quantum czars just cracked “magic state” alchemy—less noise, fewer qubits, faster ops. Translation: the ghost in the machine just got a neural upgrade. You ready for unbreakable crypto? Or unstoppable AI? 🔥

[strategictech]

IBM Says on Course to Fault-Tolerant Quantum by 2029

IBM (NYSE: IBM) unveiled what the company said is its path to build the first large-scale, fault-tolerant quantum computer, “setting the stage for practical and scalable quantum computing.”

@tonyshan #techinnovation https://bit.ly/tonyshan https://bit.ly/tonyshan_X

[jcmarchi]

Fast control methods enable record-setting fidelity in superconducting qubit

New Post has been published on https://thedigitalinsider.com/fast-control-methods-enable-record-setting-fidelity-in-superconducting-qubit/

Fast control methods enable record-setting fidelity in superconducting qubit

Quantum computing promises to solve complex problems exponentially faster than a classical computer, by using the principles of quantum mechanics to encode and manipulate information in quantum bits (qubits).

Qubits are the building blocks of a quantum computer. One challenge to scaling, however, is that qubits are highly sensitive to background noise and control imperfections, which introduce errors into the quantum operations and ultimately limit the complexity and duration of a quantum algorithm. To improve the situation, MIT researchers and researchers worldwide have continually focused on improving qubit performance. 

In new work, using a superconducting qubit called fluxonium, MIT researchers in the Department of Physics, the Research Laboratory of Electronics (RLE), and the Department of Electrical Engineering and Computer Science (EECS) developed two new control techniques to achieve a world-record single-qubit fidelity of 99.998 percent. This result complements then-MIT researcher Leon Ding’s demonstration last year of a 99.92 percent two-qubit gate fidelity. 

The paper’s senior authors are David Rower PhD ’24, a recent physics postdoc in MIT’s Engineering Quantum Systems (EQuS) group and now a research scientist at the Google Quantum AI laboratory; Leon Ding PhD ’23 from EQuS, now leading the Calibration team at Atlantic Quantum; and William D. Oliver, the Henry Ellis Warren Professor of EECS and professor of physics, leader of EQuS, director of the Center for Quantum Engineering, and RLE associate director. The paper recently appeared in the journal PRX Quantum.

Decoherence and counter-rotating errors

A major challenge with quantum computation is decoherence, a process by which qubits lose their quantum information. For platforms such as superconducting qubits, decoherence stands in the way of realizing higher-fidelity quantum gates.

Quantum computers need to achieve high gate fidelities in order to implement sustained computation through protocols like quantum error correction. The higher the gate fidelity, the easier it is to realize practical quantum computing.

MIT researchers are developing techniques to make quantum gates, the basic operations of a quantum computer, as fast as possible in order to reduce the impact of decoherence. However, as gates get faster, another type of error, arising from counter-rotating dynamics, can be introduced because of the way qubits are controlled using electromagnetic waves. 

Single-qubit gates are usually implemented with a resonant pulse, which induces Rabi oscillations between the qubit states. When the pulses are too fast, however, “Rabi gates” are not so consistent, due to unwanted errors from counter-rotating effects. The faster the gate, the more the counter-rotating error is manifest. For low-frequency qubits such as fluxonium, counter-rotating errors limit the fidelity of fast gates.

“Getting rid of these errors was a fun challenge for us,” says Rower. “Initially, Leon had the idea to utilize circularly polarized microwave drives, analogous to circularly polarized light, but realized by controlling the relative phase of charge and flux drives of a superconducting qubit. Such a circularly polarized drive would ideally be immune to counter-rotating errors.”

While Ding’s idea worked immediately, the fidelities achieved with circularly polarized drives were not as high as expected from coherence measurements.

“Eventually, we stumbled on a beautifully simple idea,” says Rower. “If we applied pulses at exactly the right times, we should be able to make counter-rotating errors consistent from pulse-to-pulse. This would make the counter-rotating errors correctable. Even better, they would be automatically accounted for with our usual Rabi gate calibrations!”

They called this idea “commensurate pulses,” since the pulses needed to be applied at times commensurate with intervals determined by the qubit frequency through its inverse, the time period. Commensurate pulses are defined simply by timing constraints and can be applied to a single linear qubit drive. In contrast, circularly polarized microwaves require two drives and some extra calibration.

“I had much fun developing the commensurate technique,” says Rower. “It was simple, we understood why it worked so well, and it should be portable to any qubit suffering from counter-rotating errors!”

“This project makes it clear that counter-rotating errors can be dealt with easily. This is a wonderful thing for low-frequency qubits such as fluxonium, which are looking more and more promising for quantum computing.”

Fluxonium’s promise

Fluxonium is a type of superconducting qubit made up of a capacitor and Josephson junction; unlike transmon qubits, however, fluxonium also includes a large “superinductor,” which by design helps protect the qubit from environmental noise. This results in performing logical operations, or gates, with greater accuracy.

Despite having higher coherence, however, fluxonium has a lower qubit frequency that is generally associated with proportionally longer gates.

“Here, we’ve demonstrated a gate that is among the fastest and highest-fidelity across all superconducting qubits,” says Ding. “Our experiments really show that fluxonium is a qubit that supports both interesting physical explorations and also absolutely delivers in terms of engineering performance.”

With further research, they hope to reveal new limitations and yield even faster and higher-fidelity gates.

“Counter-rotating dynamics have been understudied in the context of superconducting quantum computing because of how well the rotating-wave approximation holds in common scenarios,” says Ding. “Our paper shows how to precisely calibrate fast, low-frequency gates where the rotating-wave approximation does not hold.”

Physics and engineering team up

“This is a wonderful example of the type of work we like to do in EQuS, because it leverages fundamental concepts in both physics and electrical engineering to achieve a better outcome,” says Oliver. “It builds on our earlier work with non-adiabatic qubit control, applies it to a new qubit — fluxonium — and makes a beautiful connection with counter-rotating dynamics.”

The science and engineering teams enabled the high fidelity in two ways. First, the team demonstrated “commensurate” (synchronous) non-adiabatic control, which goes beyond the standard “rotating wave approximation” of standard Rabi approaches. This leverages ideas that won the 2023 Nobel Prize in Physics for ultrafast “attosecond” pulses of light.

Secondly, they demonstrated it using an analog to circularly polarized light. Rather than a physical electromagnetic field with a rotating polarization vector in real x-y space, they realized a synthetic version of circularly polarized light using the qubit’s x-y space, which in this case corresponds to its magnetic flux and electric charge.

The combination of a new take on an existing qubit design (fluxonium) and the application of advanced control methods applied to an understanding of the underlying physics enabled this result.

Platform-independent and requiring no additional calibration overhead, this work establishes straightforward strategies for mitigating counter-rotating effects from strong drives in circuit quantum electrodynamics and other platforms, which the researchers expect to be helpful in the effort to realize high-fidelity control for fault-tolerant quantum computing.

Adds Oliver, “With the recent announcement of Google’s Willow quantum chip that demonstrated quantum error correction beyond threshold for the first time, this is a timely result, as we have pushed performance even higher. Higher-performant qubits will lead to lower overhead requirements for implementing error correction.”  

Other researchers on the paper are RLE’s Helin Zhang, Max Hays, Patrick M. Harrington, Ilan T. Rosen, Simon Gustavsson, Kyle Serniak, Jeffrey A. Grover, and Junyoung An, who is also with EECS; and MIT Lincoln Laboratory’s Jeffrey M. Gertler, Thomas M. Hazard, Bethany M. Niedzielski, and Mollie E. Schwartz.

This research was funded, in part, by the U.S. Army Research Office, the U.S. Department of Energy Office of Science, National Quantum Information Science Research Centers, Co-design Center for Quantum Advantage, U.S. Air Force, the U.S. Office of the Director of National Intelligence, and the U.S. National Science Foundation.  

[materialsscienceandengineering]

Physics researchers identify new multiple Majorana zero modes in superconducting SnTe

A collaborative research team has identified the world's first multiple Majorana zero modes (MZMs) in a single vortex of the superconducting topological crystalline insulator SnTe and exploited crystal symmetry to control the coupling between the MZMs. This discovery, published in Nature, offers a new pathway to realizing fault-tolerant quantum computers. The team was led by Prof. Junwei Liu, Associate Professor in the Department of Physics at the Hong Kong University of Science and Technology (HKUST), and Prof Jinfeng Jia and Prof Yaoyi Li from Shanghai Jiao Tong University (SJTU). MZM is a zero-energy topologically nontrivial quasiparticle in a superconductor that obeys non-Abelian statistics, allowing for inequivalent braiding sequences, even though the total number of exchanges is the same. This contrasts with ordinary particles, such as electrons or photons, where different braiding always results in the same final state. This unique property protects MZMs from local perturbations, making them an ideal platform for robust fault-tolerant quantum computation.

Read more.

[jpmellojr]

IBM Says It Will Have Large-Scale Quantum Computer by 2029

IBM aims to deliver the world's first large-scale, fault-tolerant quantum computer by 2029! This is a significant milestone for quantum computing. https://jpmellojr.blogspot.com/2025/06/ibm-says-it-will-have-large-scale.html

[govindhtech]

Atom Computing is Ushering in a New Era of Quantum Research

Atom Computing

Recently, quantum computers constructed from arrays of ultracold atoms have become a major contender in the race to produce machines powered by qubits that can surpass their classical counterparts in performance. Although the first completely functional quantum processors to be programmed via the cloud have been produced by alternative hardware architectures, further advancements indicate that atom-based platforms may be superior in terms of future scalability.

This scaling benefit results from the atomic qubits being exclusively cooled, trapped, and manipulated via photonic technology. Neutral-atom quantum computers can be primarily constructed using currently available optical components and systems that have already been optimised for accuracy and dependability, eschewing the need for intricate cryogenic systems or chip fabrication processes.

A physicist at Princeton University in the United States named Jeff Thompson and his team have been developing a quantum computer based on arrays of ytterbium atoms. “The traps are optical tweezers, the atoms are controlled with laser beams and the imaging is done with a camera,” Thompson explains. “The engineering that can be done with the optical system is the only thing limiting the scalability of the platform, and a lot of that work has already been done in the industry of optical components and megapixel devices.”

Enormous atomic arrays

Many attractive properties of neutral atoms make them suitable for quantum information encoding. Firstly, they are all the same, meaning that there is no need to tune or calibrate individual qubits because they are all flawless and devoid of any flaws that could be introduced during creation. Important quantum features like superposition and entanglement are preserved over sufficiently long periods to enable computation, and their quantum states and interactions are likewise well understood and characterised.

The pursuit of fault tolerance This important development made atomic qubits a competitive platform for digital quantum computing, spurring research teams and quantum companies to investigate and improve the efficiency of various atomic systems. Although rubidium remains a popular option, ytterbium is seen by certain groups to provide some important advantages for large-scale quantum computing. Thompson argues that because ytterbium has a nuclear spin of one half, the qubit can be encoded entirely in the nuclear spin.”They found that pure nuclear-spin qubits can maintain coherence times of many seconds without special procedures, even though all atom- or ion-based qubits havegood coherence by default.”

Examining rational qubits

In the meanwhile, Lukin’s Harvard group has perhaps made the closest approach to error-corrected quantum computing to yet, collaborating with a number of academic partners and the Boston-based startup QuEra Computing. Utilising so-called logical qubits, which distribute the quantum information among several physical qubits to reduce error effects, is a critical advancement.

One or two logical qubits have been produced in previous demonstrations using different hardware platforms, but Lukin and colleagues demonstrated by the end of 2023 that they could produce 48 logical qubits from 280 atomic qubits. They were able to move and operate each logical block as a single unit by using optical multiplexing to illuminate every rubidium atom inside a logical qubit with identical light beams. This hardware-efficient control technique stops mistakes in the physical qubits from growing into a logical defect since every atom in the logical block is treated separately.

The researchers additionally partitioned their design into three functional zones to enable more scalable processing of these logical qubits. The first is utilised to ensure that these stable quantum states are separated from processing mistakes in other sections of the hardware by manipulating and storing the logical qubits, coupled with a reservoir of physical qubits that may be called upon. Next, logical qubit pairs can be “shuttled” into the second entangling zone, where two-qubit gate operations are driven with fidelity exceeding 99.5% by a single excitation laser. Each gate operation’s result is measured in the final readout zone, which doesn’t interfere with the ongoing processing duties.

Future scalability Another noteworthy development is that QuEra has secured a multimillion-dollar contract at the UK’s National Quantum Computing Centre (NQCC) to construct a version of this logical processor. By March 2025, the national lab will have seven prototype quantum computers installed, including platforms that take advantage of superconducting qubits and trapped ions, as well as a neutral-atom system based on cesium from Infleqtion (previously ColdQuanta). The QuEra system will be one of these systems.

Replenishing the supply of atoms In order to create a path to larger-scale machines, the Atom Computing team has included additional optical technologies into its revised platform. Bloom states, “They could have just bought some really big lasers if They wanted to go from 100 to 1,000 qubits.” “However, they wanted to get the array on a path where they can keep expanding it to hundreds of thousands or even a million atoms without encountering problems with the laser power.”

Combining the atomic control offered by optical tweezers with the trapping capability of optical lattices which are primarily found in the most accurate atomic clocks in the world has been the solution for Atom Computing. By adding an optical buildup cavity to create constructive interference between multiple reflected laserThese optical lattices can improve their performance by creating a subwavelength grid of potential wells via laser beam interference.”With just a moderate amount of laser power, They can create a huge array of deep traps with these in-vacuum optics,” adds.”They could rise higher, but decided to show an arrangement that traps 1,225 ytterbium.”

Read more on Govindhtech.com

[frank-olivier]

The Topological Advantage: How Anyons Are Changing Quantum Computing

The field of quantum computing has experienced a significant paradigm shift in recent years, with the emergence of topological quantum computing as a promising approach to building practical quantum computers. At the heart of this new paradigm is the concept of anyons, quasiparticles that exhibit non-Abelian statistics in two-dimensional spaces. First proposed by physicist Frank Wilczek in 1982, anyons have been extensively studied and experimentally confirmed in various systems.

The discovery of anyons and their unique properties has opened up new avenues for quantum computing, enabling the development of fault-tolerant quantum gates and scalable quantum systems. The topological properties of anyons make them well-suited for creating stable qubits, the fundamental units of quantum information. The robustness of these qubits stems from their topological characteristics, which are less susceptible to errors caused by environmental disturbances.

One of the most significant advantages of topological quantum computing is its inherent error resistance. The robust nature of anyonic systems minimizes sensitivity to local perturbations, reducing the need for complex error correction codes and facilitating scalability. Michael Freedman and colleagues first demonstrated this concept in 2003, and it has since been extensively studied.

The manipulation of anyons through braiding, where anyons are moved around each other in specific patterns, implements quantum gates that are inherently fault-tolerant. This concept was first introduced by Alexei Kitaev in 1997, and has since been extensively studied. The topological nature of braiding ensures that operations are resistant to errors, as they rely only on the topology of the braiding path, not its precise details.

Topological quantum computing has far-reaching potential applications, with significant implications for cryptography, material science, and quantum simulations. Topological quantum computing enables enhanced security protocols, insights into novel states of matter, and more efficient simulations of complex quantum systems.

Prof. Steve Simon: Topological Quantum Computing (University of Waterloo, June 2012)

Part 1

Part 2

Tuesday, October 8, 2024