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Discovery thrives on unexpected connections. This collection of highly interdisciplinary papers, published in PRX Quantum in 2024 and 2025, marks the celebration of the International Year of Quantum (IYQ). It opens with a reflection on the revolutionary ideas that shaped the last century and spotlights the most exciting research shaping the next decade of quantum science and technology. The next breakthroughs are yours to make: shape the future with us.
Click on the bars to explore the research shaping quantum science today — and tomorrow.
Editorial
Celebrating 100 years of quantum mechanics: a journey of groundbreaking discoveries and the next frontier of quantum science and technologies.
12 March 2025
The Giants That Brought Us Here
“It is delightful to read Serge’s Perspective on the development of AMO physics over the past century, focusing on laser’s revolutionary impact to the rapid and profound progress in quantum science. Serge is a dynamic pioneer and a powerful witness to these historical advances, and his account of scientific breakthroughs intertwined with personal anecdotes is simultaneously educational and entertaining. The article’s deep reflections and wide perspectives provide a great opportunity for us all to remember, digest, appreciate, and anticipate the power of quantum science and its often-surprising turn of impacts.”
— Jun Ye (JILA, USA)
The Revival of Neutral Atoms
“This work presents a transformative approach to assembling and maintaining large arrays of neutral atoms, a critical step toward scalable quantum computing and simulation. By combining optical tweezers with cavity-enhanced optical lattices, the authors achieve near-deterministic filling of atomic arrays while enabling indefinite maintenance of full occupation. This breakthrough not only enhances quantum simulation and metrology but also paves the way for midcircuit reloading—an essential capability for fault-tolerant quantum computation.”
— Alejandro González-Tudela (CSIC, Spain and PRX Quantum Associate Editor)
“This innovative work takes a difficult problem–linking remote neutral atom processors–and pushes the achievable figures of merit by orders of magnitude, providing an experimentally-realizable blueprint. Optical links between spatially separated quantum processors will be necessary to scale the size of engineered quantum systems. However, current remote entanglement protocols are more error prone and orders of magnitude slower than local two-qubit gates. This work addresses this problem and lays out an experimentally realizable path to creating remote entanglement at application-relevant rates.”
— Sara Mouradian (University of Washington, USA and PRX Quantum Associate Editor)
“To get to useful “utility-scale” quantum computing, experimental physicists designing qubit systems need to understand not just the amount but also the cause of errors in their qubits. Tsai et al. show how to do this in an array of Rydberg-atom qubits, using ab initio simulation to track and attribute the 0.29% error-per-gate observed in random circuits to four different mechanisms, and pioneering a methodology that could enhance qubit performance across many hardware platforms.”
— Robin Blume-Kohout (Sandia National Laboratories, USA)
Boosting Fluxonium Qubits with Innovation
“The large anharmonicity of the superconducting fluxonium qubit—an alternative design to the ubiquitous transmon qubit—allows for fast quantum gate operations, while its low qubit frequency reduces its susceptibility to noise. Zhang et al. realize a tunable inductive coupling between fluxonium qubits to achieve high-fidelity two-qubit gates.”
— Guido Burkard (University of Konstanz, Germany)
“Several flavors of superconducting qubit architectures have now been demonstrated with two-qubit gate fidelities of 99.9%, but time varying device properties degrade this fidelity, thus necessitating frequent recalibration. Such time varying properties are especially problematic for large scale quantum processors. This work describes a two-qubit gate on fluxonium qubits that is simple, robust, and stable, achieving high fidelities over long times without recalibration.”
— Nathalie De Leon (Princeton University, USA)
Pushing the Limits with Integrated Photonics
“The authors present a scalable, power-efficient method to overcome the tradeoff between brightness and spectral density in entangled photon pair sources. Their 2021 PRX Quantum paper used a single highly nonlinear AlGaAs-on-SiO2 ring to achieve high brightness, well beyond those in silicon-based and lithium-niobate sources, but with large THz-scale frequency spacing. Here, they reduce the spacing to 20 GHz using an array of 20 AlGaAs microrings while maintaining good brightness and high purity. Using microheater tuning with sub-GHz precision, they demonstrated precise resonance alignment or spacing that matches a target frequency grid with tens of GHz. Future on-chip integration could minimize photon losses, enabling generated entangled rates of 70 MHz. The work constitutes an innovative milestone showcasing the scalability of quantum photonics.”
— Avik Dutt (University of Maryland, USA)
Cooling Our Way to Quantum Chemistry
“In the world of ultracold quantum gases, polar molecules form a rich playground for the simulation of many-body physics and controlled quantum chemistry. The authors have pioneered the cooling, trapping, and control of a new quantum gas mixture and used it to form an exotic type of “doubly polar” molecule, lithium chromium. This type of molecule has the potential to be strongly tuned with both electric and magnetic fields, enabling a wider range of capabilities for quantum science.”
— Zoe Yan (University of Chicago, USA)
Efficient Strategies to Map Quantum Systems
“This work is an exceptional example of complexity theory meeting practical constraints, advancing the field of quantum state tomography. In times when quantum and classical methods are competing to prove or disprove quantum advantages, characterizing which states can be considered hard or simple from a learning perspective is crucial. The paper generalizes the concept of learnable quantum states and also brings new perspectives to quantum machine learning.”
— Guglielmo Mazzola (University of Zürich, Switzerland and PRX Quantum Associate Editor)
“How can we efficiently extract information from quantum states? This question is fundamental to both quantum information science and the practical use of quantum computers. ‘Triply Efficient Shadow Tomography’ introduces protocols that are not only sample-efficient but also computationally efficient and leverage two-copy measurements. It provides the first approach that is triply efficient for both local fermionic observables and all n-qubit Pauli observables, offering both practical tools and new insights into quantum information processing.”
— Kosuke Mitarai (Osaka University, Japan)
Route to Outsmarting Classical Processing
“In this paper, the authors demonstrate that translationally invariant matrix product states (MPS), a powerful ansatz for studying 1D quantum systems, can be prepared on quantum computers using constant-depth adaptive circuits. This is a surprising result given that even the simplest of MPS, such as the GHZ state, can exhibit long-range correlations. The key innovation lies in leveraging intermediate measurements and classical feedforward, features essential for fault-tolerant quantum computing, to achieve a divide-and-conquer construction of the state. This approach not only outperforms the best-known unitary circuit preparations but also paves the way for incorporating these techniques into early quantum hardware as a powerful subroutine.”
— Daniel Stilck França (INRIA, France)
“A central task in the theory of quantum computation is mapping out the boundary between those quantum computations that can be simulated efficiently classically versus those that are classically intractable. The Gottesman-Knill theorem is a foundational result in this area showing that quantum circuits consisting purely of gates from the Clifford group can be efficiently simulated classically. This work takes a significant further step by proving new quantitative bounds on the number and distribution of non-Clifford T gates that are needed to render the classical simulation of quantum circuits intractable.”
— Stephen Jordan (Google, USA)
Error Correction in Action
“This paper bridges the many attractions of quantum low-density parity-check (LDPC) codes with the physical challenge of implementing them in platforms with restricted qubit movement. The authors present an error correction protocol restricted to 2D local gates that reduces operational overheads by measuring costly nonlocal generators less frequently than others. Readers will be interested in the bilayer architecture proposal and its potential application to various qubit platforms, as well as the circuit-level analysis of the tradeoff of time overhead with code performance.”
— Christina Knapp (Microsoft, USA)
“Quantum error correction is the main route to achieving the very low error rates that are needed in many applications of quantum computing. In 1997, A. Steane pointed out that codes which allow entangling logical qubits via element-wise gates between pairs of physical qubits provide naturally fault-tolerant syndrome checks, a key step of a quantum error correction cycle. While Steane’s approach uses more physical qubits, it promises lower errors, especially on platforms with high qubit connectivity such as trapped atoms and ions. Postler et al. perform up to five sequential Steane-style error checks on a fault-tolerant logical qubit encoded in trapped ions and demonstrate a reduction in the check error compared to prior experimental approaches.”
— Marko Cetina (Duke University, USA)
“Topological quantum codes exhibit two types of stability: 1) stability of topological phases under local perturbations and 2) stability of encoded quantum information under local errors. This intriguing connection prompts us to wonder if generic quantum codes, those which cannot be supported on geometrically local lattices, may also be viewed as instances of “quantum phases”. This paper addresses this question by focusing on quantum low-density parity-check (LDPC) codes and establishing a connection between the error correction threshold of LDPC Calderbank-Shor-Steane (CSS) codes and the perturbative stability of the corresponding quantum code Hamiltonian. The authors map the decoding problem to a statistical mechanics model, which is given by the imaginary time path integral of the Hamiltonian.”
— Beni Yoshida (Perimeter Institute, Canada)
Thermodynamics: From Information to Complexity and Precision
— Martí Perarnau-Llobet (Autonomous University of Barcelona, Spain)
— Juzar Thingna (PRX Quantum Associate Editor)