Linear Optics Enables Flexible Generation of Variable Entanglement GHZ-like States

The creation of complex entangled states represents a crucial challenge in developing advanced quantum technologies, particularly for communication and computation. A team led by A. A. Melkozerov from the Russian Quantum Center, M. Yu. Saygin from Quantum Technology Center, M. V. Lomonosov Moscow State University, and S. S. Straupe from Sber Quantum Technology Center, now presents a new approach to generating a versatile class of entangled states known as GHZ-like states. Their research demonstrates a linear-optical method for creating and fusing these states, offering a way to finely tune both the efficiency of state generation and the degree of entanglement achieved. This work significantly expands the toolkit for creating entangled resources, potentially paving the way for more practical and scalable quantum communication networks and computational systems.

Generating High-Fidelity GHZ-Like Entangled States

The creation and manipulation of entangled states are fundamental to photonic quantum technologies, including advanced quantum networks and computing systems. Researchers continually seek methods to generate these states more efficiently, as current approaches often suffer from low success probabilities. A key limitation arises from the probabilistic nature of generating entanglement with light. Researchers have investigated new strategies to overcome these hurdles, focusing on a generalized form of entanglement known as GHZ-like states. These GHZ-like states represent an extension of standard Greenberger-Horne-Zeilinger (GHZ) states, allowing for variable degrees of entanglement, which is crucial for many emerging quantum algorithms and codes.

The team’s approach centers on a fusion-based method, where smaller entangled states are combined to create larger ones using probabilistic entangling measurements applied to pre-generated resource states. Modifications to standard fusion gates improve efficiency and control over the resulting entanglement. Their work demonstrates that it is possible to surpass the 50% success probability limit typically associated with fusing maximally entangled states. By carefully controlling the parameters of the modified fusion gates, researchers can tailor the degree of entanglement in the final state, enabling the generation of larger states with significantly improved efficiency, even if they are not fully maximally entangled.

The team proposes two distinct protocols for generating these GHZ-like states. The first utilizes arbitrarily entangled resource states, while the second employs specific resource states to achieve even higher efficiency. Through quantitative comparisons with existing methods, the researchers demonstrate the potential of their approach to advance quantum information processing, paving the way for more scalable and practical quantum technologies.

Photonic GHZ States via Entanglement Generation

This research details a comprehensive investigation into generating multi-qubit entangled states, specifically GHZ-like states, using photons. The study explores methods for efficiently creating these states, addressing the challenges of probabilistic entanglement generation and minimizing the number of photons required. GHZ-like states are a type of multi-qubit entanglement crucial for quantum computing and communication. The research focuses on overcoming the inherent probabilistic nature of entanglement generation, where not every attempt to create an entangled state succeeds. The team developed two schemes for generating target GHZ-like states.

The first scheme uses flexible, arbitrarily entangled resource states, while the second achieves higher efficiency by utilizing resource states with specific entanglement properties. Both approaches leverage fusion measurements to combine smaller entangled states into larger ones. The results demonstrate that the proposed methods can generate GHZ-like states with significantly fewer photons compared to existing techniques for creating maximally entangled GHZ states. The efficient method consistently outperforms the general method in terms of resource efficiency, highlighting the importance of carefully designing the resource states.

The research provides a detailed comparison to existing methods, demonstrating the advantages of the new approaches and their potential for scalability to larger numbers of qubits. The study also explores the optimization of resource state design and the use of multiplexing techniques to increase the effective success rate. These methods offer a promising path towards creating multi-qubit entangled states with high efficiency and scalability, paving the way for practical quantum technologies.

The results offer a promising pathway toward resource-efficient entangled-state generation for scalable quantum computing and communication.

Efficient Generation of GHZ-like Entangled States

This work investigates methods for creating and manipulating GHZ-like states, a class of entangled states that includes standard GHZ states as a specific case. Researchers demonstrate that these GHZ-like states can be generated and fused with higher efficiency than maximally entangled GHZ states, although this comes at the cost of reduced entanglement in the resulting states. GHZ-like states are useful in quantum teleportation protocols and are related to weighted hypergraph states. The team developed two schemes for creating target GHZ-like states, one using flexible, arbitrarily entangled resource states and the other achieving higher efficiency with resource states possessing specific entanglement degrees.

Both approaches leverage fusion measurements to combine smaller entangled states into larger ones. Boosting techniques, while enhancing performance, require additional photonic resources. The results demonstrate that GHZ-like states, with varying degrees of entanglement, can be generated and fused with higher success probabilities than standard GHZ states. The level of entanglement can be finely tuned using the modified fusion gates proposed in the study. Given recent advances in quantum states beyond the stabilizer formalism, GHZ-like states appear to be promising resources for future linear-optical quantum applications. Researchers also explored weighted graph states and their applications to spin chains, lattices, and gases, as well as methods for generating entanglement with linear optics. They investigated schemes for heralded entanglement generation, and compact linear optical schemes for creating two-qubit states, contributing to the development of more efficient and versatile quantum technologies.