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Enjoy today’s breakdown of news, research, events & jobs within quantum.

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IN TODAY’S ISSUE:

Tags: CAT QUBITS ERROR CORRECTION SILICON-BASED ALGORITHMS

• Four orders of magnitude is making headlines today: Alice & Bob and École Normale Supérieure research team have extended bit-flip error protection in cat qubits up to 10s which is 10K times (four orders of magnitude) longer than previous record

• AND researchers from the the University of Melbourne and the University of Manchester used an ion beam to irradiate undesirable silicon isotopes from spin qubits resulting in…🥁…theoretical calculations of 10K longer coherence times

• A new general quantum integration algorithm for numerical integration from the Laboratory for Advanced Computing and Intelligence Engineering in China is solving integration woes across STEM fields

• Plus, a new open-source repository from Classiq, a framework for designing equivariant QNNs, and a digital flux tuner is solving the scalability problem or superconducting quantum architecture

BRIEF BYTES

NEWS FOR THOSE IN A HURRY

• To tackle the challenge of scaling superconducting quantum computers due to cable and cooling constraints of dilution refrigerators, researchers have developed a digital flux tuner to manipulate the magnetic flux in qubits. This new quantum-classical interface technology integrates with rapid single flux quantum circuits and shows gate fidelities of up to 99.676% in simulations.

• Classiq has announced the launch of a new open-source Git repository filled with tutorials and examples for quantum computing. For anyone interested, from novice to experienced programmer, this platform is designed to promote collaboration among the quantum computing community. Classiq invites contributions and encourages the community to engage with and share the resource widely. Find the repo here.

• Researchers at the University of Basel and NCCR SPIN are using hole-spin qubits to demonstrate control over two-qubit interactions via electrostatic forces. Through this, they have achieved fast and precise spin-flip operations which are essential for quantum gates. What’s more, this silicon-chip production technique shows the potential for the magnitude of scalability needed for connecting thousands of qubits.

• Uh-oh. You remember that $620 million investment in PsiQuantum by Australian government? Turns out, Australia's National Quantum Advisory Committee was not involved in the decision. They were excluded from reviewing or advising on the investment proposal which is sparking controversy among local quantum firms and raising questions about the transparency of the government.

• A theoretical framework has been presented for designing equivariant QNNs that incorporate symmetries directly into their architecture which addresses key challenges in quantum neural network trainability and generalization. This approach can efficiently handle large or continuous symmetry groups and could mitigate common issues like barren plateaus and sample complexity.

TOP HEADLINES IN NEWS & RESEARCH

NEWS

Tags: CAT QUBITS ERROR CORRECTION

CAT QUBITS ARE CATALYZING QUANTUM PROGRESS

Progress in quantum computing is stunted by error rates that challenge the efficiency and reliability of quantum systems. Most solutions around this rely on complex (read: expensive) architectures. However, a recent paradigm shift from a collaboration between researchers at Alice & Bob and École Normale Supérieure focuses on developing qubits that inherently minimize errors, prioritizing the quality of the egg before the chicken.

In an experimental breakthrough with superconducting circuits, they successfully implemented a cat qubit with bit-flip protection times exceeding 10s, which is four orders of magnitude (10K!) improvement over previous implementations. They also managed to control the phase of quantum superpositions without compromising the bit-flip protection.

But when there is a plethora of qubit modalities on the market, what makes the cat qubit spectacular (outside of the poetic association with Schrödinger's famous thought experiment, of course)?

The unique aspect of two-photon dissipation used in cat qubits provides stability without the usual decoherence seen with other dissipation forms. This method ensures that the qubit's quantum state remains coherent even as it interacts with its environment.

While this is all well and good, one of the biggest hurdles in using cat qubits is the difficulty in measuring and manipulating them without disrupting the very protections that make them advantageous. Initially, the team detected bit flip errors every few milliseconds. Over time, they realized that many of these errors were due to their measurement techniques.

Removing ancillary systems that compromised the qubit’s integrity allowed for new protocols that did not infringe on the qubit's bit-flip protection which ultimately lead to higher fidelity in quantum state assessment.

While reducing bit-flip errors might inadvertently increase susceptibility to phase-flip errors, it can be argued that stabilizing cat qubits against bit-flips allows for researchers to solely focus on correcting phase-flips. These errors typically require less complex error correction protocols so the overall quantum error correction strategy benefits from the simplicity overall.

As simple as it sounds, this improvement was a painstaking multi-year process. Additionally, this has only been demonstrated in one cat qubit. To be practically applied, this will need to be scaled and maintained across many cat qubits.

The journey towards reliable quantum computing is an iterative one, saturated with continuous adjustments and refinements. The development of a single, stable cat qubit by the Alice & Bob's and École Normale Supérieure team is a testament to the potential of this approach. Looking forward, scaling this technology to a practical number of qubits while maintaining error resistance will be crucial.

RESEARCH

Tags: SILICON-BASED

OVERVIEW OF HIGHLY 28Si ENRICHED SILICON BY LOCALISED FOCUSED ION BEAM IMPLANTATION

The Brief Byte: Silicon crystals for spin qubits show great promise in scalable quantum computation, but they are limited by the 29Si isotope which restrains qubit coherence times. This study introduces a method to improve qubit coherence in silicon-based quantum computing by reducing the presence of the 29Si isotope through irradiation.

Breakdown:

• There is a general consensus around which facets of device architecture we need to fine-tune for wide-scale quantum advantage: qubit quality that allows for high-fidelity, increased coherence times, the ability to minimize errors at scale, and ease of fabrication/large-scale hardware manufacturing. Enter silicon. This isn’t silicon’s first rodeo with high-performance computing – silicon-based spin qubits’ compatibility with existing semiconductor fabrication techniques as well as long coherence times and high gate fidelities make them stand-out candidates for a scalable quantum computer. However, issues arise from the 29Si isotope within natural silicon. This isotope's non-zero nuclear spin interferes with electron spin qubit operations and limits coherence time as well as fidelity.

• The method introduced in this research addresses the primary barriers associated with silicon's nuclear spin by depleting detrimental isotopes like 29Si and 30Si through irradiation with a 28Si focused ion beam. The reduction in the concentration of 29Si leads to improved qubit coherence times. Further, this targeted enrichment is particularly useful in prototyping quantum computer devices that use donor spins by making sure that only the essential areas containing qubits are optimized for performance, thus making the process more efficient and effective.

• Researchers successfully demonstrated the use of a focused ion beam of 28Si++ ions to create highly enriched silicon volumes within natural silicon substrates. Through NanoSIMS analysis, they confirmed the production of a 200nm deep enriched layer with minimal 2.3ppm residual 29Si levels. This process maintains elemental purity and avoids the introduction of contaminants like carbon and oxygen during annealing as verified by TEM analysis. Also, the enriched silicon produced through this method shows potential for Hahn-echo electron coherence times to exceed 10s. This would be an improvement of more than four orders of magnitude as compared to current records. Longer coherence times would allow for more complex and error-free quantum operations.

RESEARCH

Tags: ALGORITHMS

OVERVIEW OF A GENERAL QUANTUM ALGORITHM FOR NUMERICAL INTEGRATION

The Brief Byte: This paper introduces the general quantum integration algorithm for numerical integration that can handle any continuous function by approximating it with polynomials. This algorithm encodes functions into a quantum system, uses a quantum oracle to identify relevant data points, and translates the information into a quantum state, offering a speedup as compared to classical methods.

Breakdown:

• As any undergraduate student knows well, numerical integration is a foundational tool for various applications in fields such as physics, chemistry, biology, computing, and finance. Classical algorithms for numerical integration, such as the Newton-Cotes and Monte Carlo integration method, are obstructed by high computational complexity and become ineffective as the number of interpolation nodes exceeds a certain threshold. While quantum algorithms offer potential speedups over classical methods, they often are designed for very specific functions or conditions, which limits their applicability across a broader spectrum of integration tasks. The study proposes the general quantum integration algorithm to address the limited universality and operational shortcomings of both existing classical and quantum methods.

• The algorithm uses a quantum version of the Monte Carlo integration process coupled with quantum superposition to exponentially increase representation capabilities. A quantum oracle approximates the integration function, counts the integration points, and uses amplitude amplification and phase estimation to extract high-accuracy integration values.

• By using quantum encoding and polynomial approximation, GQIA handles a broad spectrum of functions, overcomes the low generality restraints faced by other quantum algorithms and demonstrates a quadratic speedup over classical approaches. However, it’s important to note that the GQIA faces circuit depth challenges which limits its practicality on current-state quantum hardware mainly due to phase estimation. This suggests a potential area for research into simplifying or finding alternatives to phase estimation that could reduce circuit depth.

EVENTS

• Thurday, May 9 | Rigetti Computing conference call on Q1 2024 financial results

• Sunday, May 12 | Quantum Reliability: Circuit Susceptibility, Faults, and Integration Issues by Washington DC Quantum Computing Meetup

• Monday, May 13 | D-Wave conference call on Q1 2024 financial results

• Thursday, May 16 | Report on Quantum Computing in the Global South by the Centre for Quantum and Society

• Monday, May 20 | Stanford Responsible Quantum Technology Conference

• Now - May 31 | Register for Google/X-Prize Quantum Challenge

JOBS POSTED WITHIN LAST 24 HOURS

• Deloitte Quantum Readiness Strategy Consultant | Washington, DC (Hybrid)

• Quantum Futures Propulsion Engineer | California $100K -170K

• Quantum Futures Photonic Integrated Circuit Engineer | California

• USRA Scientist, Quantum | Mountain View, CA $92.9K - $146.3K

• Oak Ridge National Laboratory Postdoctoral Research Associate Neutron Scattering and Quantum Materials | Oak Ridge, TN

UNTIL TOMORROW.

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