Large-scale Rydberg atom arrays are used for highly coherent analogue quantum simulations and for digital quantum computations. However, advanced quantum protocols, such as quantum error correction, require midcircuit qubit operations, including the replenishment, reset and read-out of a subset of qubits. A compelling strategy for unlocking these capabilities is a dual-species architecture in which a second atomic species is controlled independently and entangled with the first through Rydberg interactions. Here, we realize a dual-species Rydberg array consisting of rubidium and caesium atoms and explore regimes of interactions and dynamics not accessible in single-species architectures. We achieve enhanced interspecies interactions by electrically tuning the Rydberg states close to a Förster resonance. In this regime, we demonstrate an interspecies Rydberg blockade and implement a quantum state transfer from one species to another. We then generate a Bell state between Rb and Cs hyperfine qubits through an interspecies controlled-phase gate. Finally, we combine interspecies entanglement with a native midcircuit read-out to achieve quantum non-demolition measurements. Rydberg atoms in optical tweezers are a promising platform for quantum information science. A platform composed of dual-species Rydberg arrays has been realized, offering access to unexplored interaction regimes and crosstalk-free midcircuit control.
Large-scale Rydberg atom arrays are used for highly coherent analogue quantum simulations and for digital quantum computations. However, advanced quantum protocols, such as quantum error correction, require midcircuit qubit operations, including the replenishment, reset and read-out of a subset of qubits. A compelling strategy for unlocking these capabilities is a dual-species architecture in which a second atomic species is controlled independently and entangled with the first through Rydberg interactions. Here, we realize a dual-species Rydberg array consisting of rubidium and caesium atoms and explore regimes of interactions and dynamics not accessible in single-species architectures. We achieve enhanced interspecies interactions by electrically tuning the Rydberg states close to a Förster resonance. In this regime, we demonstrate an interspecies Rydberg blockade and implement a quantum state transfer from one species to another. We then generate a Bell state between Rb and Cs hyperfine qubits through an interspecies controlled-phase gate. Finally, we combine interspecies entanglement with a native midcircuit read-out to achieve quantum non-demolition measurements. Rydberg atoms in optical tweezers are a promising platform for quantum information science. A platform composed of dual-species Rydberg arrays has been realized, offering access to unexplored interaction regimes and crosstalk-free midcircuit control.
Over the past decade, quantum information science has progressed from few-qubit demonstrations to experiments with hundreds of qubits. Neutral atom processors based on individual atoms trapped in arrays of optical tweezers have emerged as a leading candidate due to their inherent scalability and flexible connectivity. Advanced protocols like measurement-based state preparation and quantum error correction, however, require efficient crosstalk-free mid-circuit operations for the readout, reset, and replenishment of a subset of qubits. In typical single-species atom arrays, where all atoms are identical and on-resonance, such operations necessitate complex overheads from single-site addressing, coherent transport, or shielding techniques, to mitigate the qubit decoherence induced from photons scattered by neighboring atoms. To address this challenge of engineering scalable quantum architectures compatible with efficient control techniques, we introduce and implement the first dual-species atom array platform, and explore new dynamics inaccessible in single-species arrays. In this approach, two atomic species are addressed independently due to the spectral separation between their control wavelengths. We engineer two-dimensional arrays from individual rubidium (Rb) and cesium (Cs) atoms in up to 512 optical tweezers, and show that the two species can be independently trapped, cooled, and imaged with state-of-the-art performance metrics. Harnessing this intrinsic crosstalk-free control, we establish the key primitives of mid-circuit readout, real-time processing and feed-forward, and coherent mid-circuit reloading. By integrating these capabilities, we realize in-sequence, real-time correction of correlated phase errors via a spectator qubit protocol. Next, we excite atoms to Rydberg states in the Förster regime, accessing hitherto unobserved enhanced interspecies Rydberg interactions, and program them to implement the first interspecies CNOT gate. We combine this multispecies entanglement with mid-circuit readout to achieve quantum non-demolition measurement of a Rb-qubit using an auxiliary Cs-qubit, circumventing physical qubit transport. Finally, leveraging the two qubit modalities, we present the first experimental demonstration of quantum cellular automata in atom arrays using only global addressing, and prepare a 17-qubit Cs cluster state with Rb-mediated interactions. The dual-species platform and techniques established in this thesis pave the way toward measurement-based algorithms and real-time feedback control in large-scale quantum systems.
The ability to locally control and measure subsets of ancilla qubits in an efficient and crosstalk-free manner is a key ingredient in quantum error correction (QEC). Dual-species neutral atom arrays offer an ideal implementation of these capabilities, enabling independent state preparation, manipulation, and detection on each species. In this work, we realize such a dual-species Rydberg array of Na and Cs atoms trapped in co-localized 2D optical tweezer arrays, using Na as an ancilla to measure stabilizers of surrounding Cs data qubits. We identify the finite interspecies Rydberg-Rydberg interaction strength as a practical obstacle to high-fidelity multi-body entanglement and show that, by tuning the Rabi frequency and the detuning of the Rydberg driving field, the resulting geometric phase error can be compensated. This yields a protocol for simultaneous, non-destructive, in situ stabilizer readout of multiple data qubits via global pulses alone. Using this protocol, we demonstrate non-destructive measurement of Pauli-Z stabilizers on four-qubit Cs plaquettes via a single global Rydberg pulse sequence. Our results demonstrate dual-species tweezer arrays as a promising route towards scalable QEC and open the door to new quantum control protocols leveraging both interspecies and intraspecies interactions.
Optical tweezer arrays of neutral atoms have emerged as a versatile platform for analog quantum simulation and digital quantum computation, combining scalability, reconfigurable geometry, and flexible microscopic control. In the first part of this work, we develop a 133Cs Rydberg simulator and demonstrate coherent Rydberg excitation in a rearrangeable array of more than 100 atoms. We then use this platform to probe critical many-body physics, extracting the scaling dimensions of the Ising universality class from an adiabatically prepared critical state. Dual-species arrays extend these capabilities by introducing spectroscopic selectivity and independently tunable interspecies interactions. Motivated by these opportunities, we develop a dual-species Rydberg array of 23Na and 133Cs atoms. The large separation between the optical transitions of the two species allows qubits encoded in one species to be cooled, trapped, imaged, and excited while the other species remains largely undisturbed. At the same time, strong van der Waals interactions provide a programmable coupling between the two arrays. We use this platform to demonstrate a proof-of-principle multi-qubit stabilizer readout based on an interaction-compensated protocol. In this setting, spectroscopic separation becomes an architectural advantage: it enables in-situ ancilla control and readout without requiring atom transport between separate interaction and measurement zones. Consequently, a multi-qubit entangling operation that would otherwise be decomposed into a sequence of two-qubit gates can be implemented as a native, effectively constant-depth primitive. These results point toward faster and more scalable syndrome extraction in neutral-atom quantum error correction, and establish dual-species Rydberg arrays as a promising architecture connecting programmable quantum simulation with fault-tolerant quantum computation.
Abstract The ability to locally control and measure subsets of ancilla qubits in an efficient and crosstalk-free manner is a key ingredient in quantum error correction (QEC). Dual-species neutral atom arrays offer an ideal implementation of these capabilities, enabling independent state preparation, manipulation, and detection on each species. In this work, we realize such a dual-species Rydberg array of Na and Cs atoms trapped in co-localized 2D optical tweezer arrays, using Na as an ancilla to measure stabilizers of surrounding Cs data qubits. We identify the finite interspecies Rydberg-Rydberg interaction strength as a practical obstacle to high-fidelity multi-body entanglement and show that, by tuning the Rabi frequency and the detuning of the Rydberg driving field, the resulting geometric phase error can be compensated. This yields a protocol for simultaneous, non-destructive, in-situ stabilizer readout of multiple data qubits via global pulses alone. Using this protocol, we demonstrate non-destructive measurement of Pauli-Z stabilizers on four-qubit Cs plaquettes via a single global Rydberg pulse sequence. Our results demonstrate dual-species tweezer arrays as a promising route towards scalable QEC and open the door to new quantum control protocols leveraging both interspecies and intraspecies interactions.
We demonstrate an inter-species entangling Rydberg gate between rubidium (Rb) and cesium (Cs) atoms with fidelity F=0.975±0.002. The two-species atom array enables in-place quantum non-demolition (QND) qubit measurements which are a key capability for quantum error correction. We demonstrate this functionality with multi-atom error syndrome measurements achieving QND measurement fidelities of FQND=0.933(12) and 0.865(17) for two- and three-qubit plaquettes, respectively.
This thesis describes experimental and theoretical work towards a novel dual species platform for Rydberg quantum information processing employing ultracold samples of potassium (K) and rubidium (Rb) atoms. The dual-species setup combined with the possibility of deploying arrays of ultracold atomic ensembles trapped in optical tweezers will pave the way for a new generation of Rydberg single-photon optical transistors with high input photon rate. Firstly, by using degenerate fermionic 40K samples as the storage medium one can take advantage of the Pauli exclusion principle which offers protection against loss and dephasing mechanisms of Rydberg polaritons, while the bosonic 87Rb species can be used as a benchmark. Secondly, simultaneously trapping nearby ensembles of the two species opens up the possibility of creating strong interactions between photons of different ”colours”, as well as the independent control of parameters of the atomic storage medium. A theoretical study conducted in the first part of this thesis reveals multiple experimentally accessible pair combinations of K and Rb atoms in their respective Rydberg states which have high interaction strength. These K-Rb pair states offer long-range interaction suitable for such a spatially isolated transistor setup. The subsequent part presents experimental work towards a dual species Rydberg optical transistor. This includes the establishment of a laser system to access Rydberg states in both species, and a feedback system to reduce atom number fluctuations. Lastly, non-destructive measurements of Rydberg states, using electromagnetically induced transparency and the newly established setup, are presented for ultracold samples of 40K and 87Rb.