4-to-2 Quantum Code Achieves Supremacy Over Classical Methods

Researchers Rajdeep Paul, Prabuddha Roy, and A. Pan report a specific instance of quantum supremacy using a 4-to-1 code, in which four input bits are compressed into either one or two qubits, with performance exceeding both classical random-access codes and existing quantum methods. This achievement concerns more than faster communication; the team’s approach, detailed in a recent preprint, relies on pre-shared entanglement between communicating parties, a departure from standard quantum communication protocols. The researchers extended their analysis to demonstrate potential advantages in n-to-n-2 codes, suggesting scalability beyond the initial demonstration. This work isn’t simply a quantum code outperforming classical methods; it’s a demonstration with a well-defined size, reducing four input bits to either one or two output bits, with the advantage definitively proven.

This research builds on the random-access code framework, where Alice encodes inputs and sends qubits to Bob, but introduces the critical element of prior entanglement, enabling a new level of control and certification within the quantum communication channel and opening possibilities for more secure and reliable quantum networks. Researchers focused on the 4-to-1 entanglement-assisted PMRAC, with l taking values 1 and 2, deriving optimal quantum success probabilities analytically. The researchers also exhibit the addition of a verification layer to the quantum process. Their analysis extends to the 5-to-1 PMRAC, establishing upper bounds on success probabilities for l = 1, 2, and 3, and further demonstrating an advantage in the n-to-n-2 case for arbitrary n. This work, submitted for publication, highlights a semi-device-independent approach to quantum communication, where prior entanglement is key to achieving and verifying quantum capabilities, potentially influencing future secure communication designs. Source: https://arxiv.org/abs/2607.10273 Stay currentSee today’s quantum computing news on Quantum Zeitgeist for the latest breakthroughs in qubits, hardware, algorithms, and industry deals. Tags: Ivy Delaney Ivy Delaney has been working with neural networks and machine learning since the mid-nineties, back when a couple of hidden layers and a long afternoon of training counted as ambitious. She has watched the field go from academic curiosity to the thing quietly running underneath everything, and she brings that long view to quantum computing.

For Quantum Zeitgeist she covers the ground where the two fields meet. That means quantum machine learning and the variational algorithms it leans on, and it also means the less glamorous but more interesting story of classical machine learning already doing real work inside quantum machines, decoding error-correcting codes, calibrating noisy hardware and learning the error models that simulators depend on. She writes about the hardware those algorithms have to run on too, and about the post-quantum cryptography scramble that the same hardware has set off. Her stories typically start with the paper, whether that is peer-reviewed work, conference proceedings or an arXiv preprint, with the source linked so you can hold a claim up against the research it came from. She is unimpressed by benchmarks that will not say what they beat, and by demonstrations that only work in the press release. Latest Posts by Ivy Delaney: Thawed Gaussian Dynamics Unifies Quantum & Classical Simulations July 14, 2026 Yale Researchers Couple Microwave Photons to 110 GHz Phonons July 14, 2026 Levitated Optomechanics Squeeze Phonon Lasers by 3.15 dB July 14, 2026