We introduce the concept of quantum actuators as mediators for globally controlled quantum computation. Auxiliary quantum systems act as controllable elements that transiently store and release interaction energy, enabling the selective activation of multi-qubit gates within globally driven architectures. During compilation they remain passive and require no fine-grained local control, while during operation they allow for controlled activation of interactions and directional flow of quantum information. We provide a framework for embedding quantum actuators in globally controlled processors, showing how they enhance connectivity, enable long-range entangling operations, and bridge distant regions without increasing local control overhead. We discuss physical implementations and architectural strategies illustrating how these elements extend the capabilities of global-control schemes. A complementary interpretation in terms of quantum batteries naturally emerges, connecting global-control architectures with concepts from quantum thermodynamics while highlighting the distinct operational role of quantum actuators.
We introduce the concept of quantum actuators as mediators for globally controlled quantum computation. Auxiliary quantum systems act as controllable elements that transiently store and release interaction energy, enabling the selective activation of multi-qubit gates within globally driven architectures. During compilation they remain passive and require no fine-grained local control, while during operation they allow for controlled activation of interactions and directional flow of quantum information. We provide a framework for embedding quantum actuators in globally controlled processors, showing how they enhance connectivity, enable long-range entangling operations, and bridge distant regions without increasing local control overhead. We discuss physical implementations and architectural strategies illustrating how these elements extend the capabilities of global-control schemes. A complementary interpretation in terms of quantum batteries naturally emerges, connecting global-control architectures with concepts from quantum thermodynamics while highlighting the distinct operational role of quantum actuators.
We present a comprehensive framework for constructing various architectures of globally driven quantum computers, with a focus on superconducting qubits. Our approach leverages static inhomogeneities in the Rabi frequencies of qubits controlled by a common classical pulse -- a technique we refer to as the "crossed-qubit" method. We detail the essential components and design principles required to realize such systems, highlighting how global control can be harnessed to perform local operations, enabling universal quantum computation. This framework offers a scalable pathway toward quantum processors by striking a balance between wiring complexity and computational efficiency, with potential applications in addressing current challenges to scalability.
Universal quantum computation requires the implementation of arbitrary control operations on the quantum register. In most cases, this is achieved by external control fields acting selectively on each qubit to drive single-qubit operations. In combination with a drift Hamiltonian containing interactions between the qubits, this allows the implementation of arbitrary gate operations. Here, we demonstrate an alternative scheme that does not require local control for all qubits: we implement one- and two-qubit gate operations on a set of target qubits indirectly, through a combination of gates on directly controlled actuator qubits with a drift Hamiltonian that couples actuator and target qubits. Experiments are performed on nuclear spins, using radio-frequency pulses as gate operations and magnetic-dipole couplings for the drift Hamiltonian.
Superconducting circuits are a leading platform for quantum computation and quantum simulation. Interactions are typically mediated by pairwise coupling elements between nearest neighbor qubits. The development of tunable couplers has been essential to achieving high fidelity entangling gates alongside high fidelity single qubit gates in quantum processors. In quantum simulators, tunable coupling allows flexibility in emulating different systems and the exploration of different parameter regimes of those models in a single physical device. Distributed element circuitry has enabled long range coupling and leveraging of interference effects and spatial mode variations to enhance device performance. In this thesis I will discuss work towards developing a distributed element tunable coupling circuit: a transmission line cavity terminated by SQUIDs, which serve as flux tunable impedances, at either boundary. With this device we hope to integrate the dynamic programmability of interactions mediated by a tunable coupler with the long-range, multi-qubit coupling enabled by distributed transmission lines in a single system. We experimentally demonstrate the core functionality, including tunability of the coupling rates, programmability of the connectivity graph, and parallel operation via multiplexing. Additionally, we utilize this device to explore photon blockade effects in the Tavis-Cummings Model, highlighting the value of tunability and controllability when simulating novel light-matter interactions in highly connected systems. These results contribute to ongoing research towards designing, calibrating, and operating highly connected superconducting circuit systems. Devices with high connectivity enable more efficient circuit compilation and are useful as quantum routers in quantum networks. In recent years, understanding the role of connectivity in quantum error correction has emerged as an important research focus. There is ongoing work evaluating the tradeoff between performance and connectivity in real devices. The development of coupling architectures that enable denser and/or longer range connectivity will play a critical role in optimizing this tradeoff.
The River Theory introduces a conceptual and computational framework for modeling reality as a dynamic probabilistic field in which multiple observers interact locally without determining the system globally. The model is based on the assumption that observable states do not arise solely from isolated measurements, but may instead emerge as collective outcomes of interacting observers embedded within the same probabilistic structure. At its core, the framework combines: a natural probabilistic flow, represented as a gradient-driven dynamic (∇P), local perturbations induced by observers, modeled as bounded deviations, and interaction terms between agents, enabling emergent collective behavior. This leads to a generalized dynamical formulation: dX/dt = ∇P(X,t) + Σ αᵢ(t)·uᵢ(X,t) where the system evolves as a balance between underlying probabilistic attractors and constrained local interventions. 🧠 Conceptual Scope The work is positioned within the domain of: complex systems and multi-agent dynamics probabilistic modeling and emergent behavior decision processes under constraints and explores potential interpretative connections with foundational questions in quantum mechanics, particularly regarding state selection and observer-dependent phenomena. 🧪 Numerical Simulation To support the conceptual framework, a numerical simulation of a multi-agent system in a two-dimensional probabilistic field is presented. The simulation demonstrates: spontaneous convergence of agent trajectories, reduction of spatial dispersion over time, emergence of shared stable configurations. These results suggest that collaborative collapse-like behavior can arise from local interactions alone, without requiring centralized control or external coordination. ⚠️ Limitations The proposed model is intentionally simplified and should be interpreted as a proof of concept rather than a complete physical theory. In particular: it does not incorporate explicit energetic constraints, it is not calibrated against experimental data, and it does not claim direct equivalence with established quantum formalism. 🚀 Perspective The River Theory is intended as an exploratory framework that may contribute to: alternative interpretations of state selection processes, modeling of observer-dependent systems, and further investigation of collective dynamics in probabilistic environments. It represents a first step toward a more general approach in which the observer is treated as an active, dynamic component of the system rather than a purely passive entity.
The River Theory introduces a conceptual and computational framework for modeling reality as a dynamic probabilistic field in which multiple observers interact locally without determining the system globally. The model is based on the assumption that observable states do not arise solely from isolated measurements, but may instead emerge as collective outcomes of interacting observers embedded within the same probabilistic structure. At its core, the framework combines: a natural probabilistic flow, represented as a gradient-driven dynamic (∇P), local perturbations induced by observers, modeled as bounded deviations, and interaction terms between agents, enabling emergent collective behavior. This leads to a generalized dynamical formulation: dX/dt = ∇P(X,t) + Σ αᵢ(t)·uᵢ(X,t) where the system evolves as a balance between underlying probabilistic attractors and constrained local interventions. Conceptual Scope The work is positioned within the domain of: complex systems and multi-agent dynamics probabilistic modeling and emergent behavior decision processes under constraints and explores potential interpretative connections with foundational questions in quantum mechanics, particularly regarding state selection and observer-dependent phenomena. Numerical Simulation To support the conceptual framework, a numerical simulation of a multi-agent system in a two-dimensional probabilistic field is presented. The simulation demonstrates: spontaneous convergence of agent trajectories, reduction of spatial dispersion over time, emergence of shared stable configurations. These results suggest that collaborative collapse-like behavior can arise from local interactions alone, without requiring centralized control or external coordination. Limitations The proposed model is intentionally simplified and should be interpreted as a proof of concept rather than a complete physical theory. In particular: it does not incorporate explicit energetic constraints, it is not calibrated against experimental data, and it does not claim direct equivalence with established quantum formalism. Perspective The River Theory is intended as an exploratory framework that may contribute to: alternative interpretations of state selection processes, modeling of observer-dependent systems, and further investigation of collective dynamics in probabilistic environments. It represents a first step toward a more general approach in which the observer is treated as an active, dynamic component of the system rather than a purely passive entity.