Quantum Computing
Learn about quantum algorithms, quantum information theory, and quantum computing applications
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Thu, Feb 19
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Why does quantum physics use complex numbers at all? Is it possible to come up with Quantum physics that only uses real numbers?
This is inspired by the recent [quanta article](https://www.quantamagazine.org/physicists-take-the-imaginary-numbers-out-of-quantum-mechanics-20251107/) on how Physicists took the i out of Schrodinger's equation. However, they replaced i with a structure isomorphic to the complex numbers, so did nothing change? I'm curious why Quantum physics even needs complex numbers at all. In the article, it said Schrodinger didn't like the i in his wave function and wanted to get rid of it. Why isn't this p
MerLean: An Agentic Framework for Autoformalization in Quantum Computation
We introduce MerLean, a fully automated agentic framework for autoformalization in quantum computation. MerLean extracts mathematical statements from \LaTeX{} source files, formalizes them into verified Lean~4 code built on Mathlib, and translates the result back into human-readable \LaTeX{} for semantic review. We evaluate MerLean on three theoretical quantum computing papers producing 2,050 Lean declarations from 114 statements in total. MerLean achieves end-to-end formalization on all three papers, reducing the verification burden to only the newly introduced definitions and axioms. Our results demonstrate that agentic autoformalization can scale to frontier research, offering both a practical tool for machine-verified peer review and a scalable engine for mining high-quality synthetic data to train future reasoning models. Our approach can also be generalized to any other rigorous research in mathematics and theoretical physics.
Quantum Cellular Automata: The Group, the Space, and the Spectrum
Over an arbitrary commutative ring $R$, we develop a theory of quantum cellular automata. We then use algebraic K-theory to construct a space $\mathbf{Q}(X)$ of quantum cellular automata (QCA) on a given metric space $X$. In most cases of interest, $π_0 \mathbf{Q}(X)$ classifies QCA up to quantum circuits and stabilization. Notably, the QCA spaces are related by homotopy equivalences $\mathbf{Q}(*) \simeq Ω^n \mathbf{Q}(\mathbb{Z}^n)$ for all $n$, which shows that the classification of QCA on Euclidean lattices is given by an $Ω$-spectrum indexed by the dimension $n$. As a corollary, we also obtain a non-connective delooping of the K-theory of Azumaya $R$-algebras, which may be of independent interests. We also include a section leading to the $Ω$-spectrum for QCA over $C^*$-algebras with unitary circuits.
Bichromatic Quantum Teleportation of Weak Coherent Polarization States on a Metropolitan Fiber
As quantum technologies mature, telecommunication operators have a clear opportunity to unlock and scale new services by providing the connectivity layer that links quantum computers, sensors, clocks, and other quantum devices. Realizing this opportunity requires demonstrating quantum networking protocols, including quantum teleportation, under real-world conditions on existing telecom infrastructure. In this work, we demonstrate quantum teleportation over Deutsche Telekom's metropolitan fiber testbed in Berlin using commercial components deployed at the telecom datacenter. A local Bell-state measurement between 795 nm photons from a weak coherent source and from a bichromatic warm-atom entangled photon source enables conditional state transfer onto an O-band photon, which is transmitted through a 30-km field-deployed fiber loop under real-world environmental conditions. The teleported state is reconstructed after propagation via state tomography, achieving an average teleportation fidelity of 90\% on the deployed link. System performance is evaluated in both the absence and the presence of co-propagating C-band classical traffic within the same fiber, demonstrating compatibility with wavelength-division multiplexed telecom infrastructure carrying live data channels.
Intermodal quantum key distribution over an 18 km free-space channel with adaptive optics and room-temperature detectors
Intermodal quantum key distribution at telecom wavelengths provides a hybrid interface between fiber connections and free-space links, both essential for the realization of scalable and interoperable quantum networks. Although demonstrated over short-range free-space links, long-distance implementations of intermodal quantum key distribution remain challenging, due to turbulence-induced wavefront aberrations which limit efficient single-mode fiber coupling at the optical receiver. Here, we demonstrate a real-time intermodal quantum key distribution field trial over an 18 km free-space link, connecting a remote terminal to an urban optical ground station equipped with a 40 cm-class telescope. An adaptive optics system, implementing direct wavefront sensing and high-order aberration correction, enables efficient single-mode fiber coupling and allows secure key generation of 200 bit/s using a compact state analyzer equipped with room-temperature detectors. We further validate through experimental data a turbulence-based model for predicting fiber coupling efficiency, providing practical design guidelines for future intermodal quantum networks.
Photons Encode Quantum Data with Improved Stability
Researchers have successfully encoded quantum information onto the properties of single photons using a novel technique involving light’s frequency and timing, paving the way for more robust and scalable photonic quantum computers.
Quantum Circuits Simulate Electron Microscope Images Accurately
Researchers have developed a quantum computing framework that accurately simulates transmission electron microscopy images, potentially accelerating analysis of materials by efficiently calculating image features inaccessible to conventional methods.
Quantum Codes Boost Computer Scalability with Logic Design
Researchers have developed RASCqL, a novel computer architecture utilising low-density parity-check codes that reduces the size of quantum computing circuits by up to 35% and maintains comparable processing speeds to existing methods, paving the way for more scalable quantum computation.
Quantum Error Correction Faces Fundamental Limit for Qubits
Researchers have demonstrated that constructing error-correcting quantum codes capable of performing all Clifford operations on more than one qubit using standard architectural approaches is fundamentally impossible.
Quantum Walks Boost Security on Early Computers
Researchers have demonstrated a quantum cryptographic protocol utilising chaotic quantum walks on cyclic graphs that, despite functioning reliably under ideal conditions and on near-term quantum computers, reveals eavesdropping attempts through detectable disturbances in its periodic signal.
Quantum Dots Enable Faster, Scalable Qubit Gates
Researchers have demonstrated that manipulating the spin of a qubit as it moves between quantum dots with differing magnetic properties allows for the creation of complex quantum gates, including a generalised Hadamard gate, without the need for complex high-frequency control.
Quantum Algorithm Boosts Portfolio Returns with Constraints
Researchers have demonstrated a quantum-inspired algorithm, utilising a novel constraint-preserving approach, that generated a portfolio with a Sharpe Ratio of 1.
Simplified Quantum Calculations Tackle Complex Molecules
Researchers have developed a modified quantum algorithm, quadratic unitary coupled cluster, that accurately simulates complex molecular behaviour by strategically prioritising the most critical computational steps, significantly reducing the resources needed compared to existing methods.
Quantum Circuits Learn System Behaviour from Data Alone
Researchers have developed a new method, SIQHDy, which accurately recreates the behaviour of quantum systems by learning the underlying rules from limited observational data using a streamlined circuit-based approach.
Machine Learning Boosts Heat Equation Solutions
Researchers have demonstrated that hybrid classical-quantum neural networks can effectively solve heat equations by integrating quantum circuits to enhance data encoding and improve the modelling of parabolic partial differential equations with potential applications for near-term quantum hardware.
Quantum Repeaters Gain Programmable Control Via New Architecture
Researchers have demonstrated a new programmable architecture for quantum repeaters utilising the nuclear spin of nitrogen-vacancy centres to enable both conventional and coherent control of data qubits, facilitating advanced protocols and diagnostics unavailable in current systems.
Quantum Measurements Mapped to Surgical Link Operations
Researchers have demonstrated that single-qubit measurements on one-dimensional cluster states can be precisely mapped onto geometric operations using a framed ribbon model, revealing how measurement phases manifest as twists within the ribbon structure and offering a new way to understand entanglement transformations.
Quantum System Tracks Single Photons over 16 Metres
Researchers have successfully created and controlled the behaviour of single quantum particles within a programmable, synthetic frequency lattice using superconducting circuits and a 16-metre cable, demonstrating quantum random walks and unidirectional frequency conversion.
Circuits Describe Qubit States and Steane Code Measurements
Researchers explored the foundational mathematics of quantum computation, demonstrating the Steane code as a key example within the circuit model to illustrate entanglement and qubit manipulation.
Faster Quantum Error Correction Unlocks Complex Codes
Researchers have devised a new, computationally efficient decoding method for graph codes, a type of quantum error correction, that leverages the predictable structure of post-measurement quantum states to achieve optimal performance at initial decoding stages without requiring complex calculations.
Quantum Chip Integrates Key Functions for Data Processing
Researchers have developed a single silicon chip integrating all necessary components to generate, control and manipulate high-dimensional quantum states using frequency-bin encoding, achieving Bell-state fidelity of 0.
Quantum Learning Agent Infers Hidden Data with Limited Interactions
Researchers have demonstrated that a streamlined hybrid reinforcement learning agent can reliably decipher hidden information encoded within quantum circuits using minimal resources, surpassing both classical and more complex quantum-enhanced approaches in challenging, noise-affected scenarios.
Study Reveals Heating Source in Quantum Dot Qubits via Two-Level Fluctuators
Voltage pulses, necessary for operating semiconductor spin qubits, dissipate heat and reduce gate fidelities, but the source of this pulse heating remains unknown. This study measures pulse heating in Si quantum dots by observing how voltage pulses affect two-level fluctuators, revealing a link to accumulated electrons near the gates.
D-Wave (NYSE: QBTS) Schedules Q4 & FY2025 Earnings Release
D-Wave Quantum Inc. (NYSE: QBTS) will release its fourth quarter and full fiscal year 2025 financial results on February 26, 2026, before market open, and will discuss findings on a conference call. The company, a dual-platform quantum computing provider, will make the press release available on its Investor Relations website.
MicroCloud Hologram (HOLO) Unveils Quantum Algorithm for Secure Financial Networks
MicroCloud Hologram Inc. has introduced a quantum intelligent consensus algorithm, integrating quantum computing to enhance the security and scalability of financial internet nodes in edge computing networks. This innovation aims to strengthen system stability, offering key support for the convergence of edge computing and financial services.
WiMi Hologram Cloud Unveils Quantum-Classical AI Model for Image Classification
WiMi Hologram Cloud Inc. has introduced a novel hybrid quantum-classical Inception neural network model designed for image classification, integrating quantum computing with classical deep learning. This new architecture aims to improve performance, efficiency, and robustness by leveraging quantum computing’s feature expression capabilities while maintaining engineering practicality.
Qunnect Demonstrates First Metro-Scale Quantum Network with Cisco, Exceeds Previous Benchmarks by 10,000x
Qunnect and Cisco have demonstrated the first metro-scale quantum entanglement swapping over deployed commercial fiber, a key step toward scalable quantum networks. Achieving record swapping rates exceeding previous benchmarks by 10,000x, this milestone validates a new model for scaling quantum networks through commercial data centers.
Quantonation Closes €220M Fund, Becoming Largest Dedicated Quantum Investment Firm
Quantonation Ventures has closed a €220 million fund, becoming the largest dedicated quantum investment firm globally. This oversubscribed fund will accelerate the transition of quantum and physics-based technologies from research into real-world infrastructure and industrial deployment.
AQT Arithmos Quantum Technologies Launches Real-World Testing Program, Starting March 31, 2026
AQT Arithmos Quantum Technologies will begin real-world testing of its quantum hybrid systems on March 31, 2026, aiming to move practical quantum computing beyond the laboratory. This program utilizes advanced quantum mechanics and mathematical models to demonstrate the viability of next-generation quantum hybrid technologies.
Exotic States Found in Complex Quantum Systems
Researchers have demonstrated a novel experimental setup and theoretical analysis revealing a previously unseen quantum state, analogous to the Yu-Shiba-Rusinov state, within a specifically engineered, non-Hermitian system exhibiting unusual electrical conductance at low temperatures.
Quantum Computing Yields Comparable Accuracy with Six Models
Researchers demonstrated that utilising a quantum processor, rather than its simulation, for machine learning improves prediction accuracy and stability by applying a natural form of data compression and reducing feature complexity.
Polaritons Reveal New Control over Quantum Interactions
Researchers have demonstrated that manipulating light-matter interactions within a specially designed superconducting circuit can slow the decay of quantum correlations, effectively enhancing the system’s ability to maintain quantum information.
Faster Quantum Computing Cuts Costs with New Methods
Researchers have developed new algebraic methods for optimising quantum circuit design, achieving comparable or improved results for minimising computational steps with significantly reduced processing power, completing circuits on a single CPU in under a minute that previously required thousands of specialised processors.
New Codes Boost Quantum Computer Error Correction
Researchers have developed a new technique for building quantum error-correcting codes by combining existing codes, resulting in improved performance and reduced error rates in quantum computations.
Quantum Computing Boosts Healthcare Data Security and Speed
Researchers are developing quantum-enhanced digital twins to overcome limitations in scalability and security, potentially enabling more effective real-time patient monitoring and personalised healthcare through advanced computational modelling.
Quantum States Transferred with Improved Accuracy and Speed
Researchers have developed a geometric pulse-shaping technique for quantum systems that allows for rapid and accurate transfer between energy levels, exceeding the limitations of traditional slow-change methods and simplifying optimisation to a solvable equation.
SEALSQ and Lattice Deliver Unified TPM-FPGA Architecture for Post-Quantum Security
SEALSQ Corp (NASDAQ: LAES) and Lattice Semiconductor (NASDAQ: LSCC) have announced a collaboration to integrate advanced post-quantum cryptography (PQC) into select Lattice FPGA solutions using a unified TPM-FPGA architecture. This collaboration addresses the urgent requirement for quantum-resistant security in mission-critical edge computing and industrial infrastructure. By combining SEALSQ’s specialized post-quantum hardware with Lattice’s low-power, secure [...] The post SEALSQ and Latti...
Qunnect and Cisco Demonstrate Quantum Entanglement over a Quantum Network in New York City
In a continued advance in quantum networking Qunnect has teamed up with Cisco to demonstrate high-speed, high-fidelity entanglement swapping on their GothamQ network in New York City. The portion of the GothamQ network, pictured above, is arranged is a hub-and-spoke topology. S1 and S2 shown in the picture are independent entanglement sources located in Brooklyn [...] The post Qunnect and Cisco Demonstrate Quantum Entanglement over a Quantum Network in New York City appeared first on Quantum...
IBM Ventures Invests in SQK and QodeX Quantum for Specialized Software Development
IBM Ventures has announced new investments in SQK and QodeX Quantum, two early-stage startups participating in the Alchemist Chicago deep tech accelerator. These investments represent a strategic move by IBM to bolster the quantum software ecosystem by supporting founders who are transitioning theoretical breakthroughs into industrial applications. Both startups were selected from the Duality accelerator [...] The post IBM Ventures Invests in SQK and QodeX Quantum for Specialized Software De...