Embedded Files
Quantum hardware architecture
Quantum hardware architecture
However, enabling entanglement between any pair of qubits remains a major challenge. Direct entangling gates are limited to qubits that are close enough to interact. To reach beyond that range, several strategies have been explored. Photonic interconnects offer a way to distribute entanglement over long distances, but they suffer from inefficient matter-photon conversion. This inefficiency occurs twice—once at each end—making them impractical for increasing connectivity within a module or between nearby quantum zones. Mechanical transport methods, such as moving neutral atoms or trapped ions, can improve entanglement rates but are constrained by slow transport speeds. These rates are still three orders of magnitude slower than two-qubit gate operations. Gate-based approaches provide an alternative route. However, the required SWAP gate is typically not native to the hardware. For example, it often decomposes into three CNOT gates, adding additional gate overhead.
Directional Transport in Rydberg Atomic Arrays
Directional Transport in Rydberg Atomic Arrays
We propose an approach to control the flow of Rydberg excitations without the need for local addressing, simplifying experimental implementation while achieving fidelities comparable to previous schemes. Our method leverages distance-dependent Rydberg-Rydberg interactions by arranging atoms with unequal spacings, so that the resonant condition for each site depends on the configuration of nearby excitations. By dynamically adjusting a global laser detuning, we offset these shifts and steer excitations along predefined routes. This combination of alternating atomic spacing and temporally modulated global driving enables programmable quantum transport that is both scalable and fast, with hopping speeds comparable to typical two-qubit gates. It allows quantum information, encoded in ground-Rydberg qubits, to move between spatially separated zones, even when each zone uses a different encoding, as long as it can be efficiently mapped to the transport basis. The approach is experimentally feasible, and as an experimental group, we aim to realize it in near-term implementations.
Ref: Yupeng Wang, Junjie Wang, Aishik Panja, Xinghan Wang, and Qi-Yu Liang, "Directional transport in Rydberg atom arrays via kinetic constraints and temporal modulation", Phys. Rev. Research 7, L022035 (2025)
Figure 1: Rydberg blockade (a) and antiblockade (b) of two atoms. The first (“seed”) atom is excited on resonance. The second atom is excited off-resonantly with a detuning Δ. The resonant condition is met when the pair-state interaction energy compensates the detuning, i.e. V = Δ. The pink shaded area marks the interatomic distances within the excitation linewidth (grey shaded area).
Rydberg antiblockade
Rydberg antiblockade
Individual cold atoms trapped in optical tweezers have emerged to be a leading quantum computing platform. Rydberg blockade is a key ingredient in engineering atomic interactions and thereby enabling multi-qubit entangling gates. Within the blockade radius, interactions between Rydberg atoms cause an energy shift that moves a pair of Rydberg atoms out of resonance with the laser, thus preventing multiple Rydberg excitations (Fig. 1(a)). Conversely, Rydberg antiblockade, also known as facilitated excitation, involves off-resonant coupling toRydberg states. This mechanism relies on interactions to bring pair states into resonance at specific interatomic distances. Facilitated excitation is typically “seeded” by resonantly exciting one or a few Rydberg atoms. Following this, the driving laser is detuned by an amount (Δ) significantly greater than the Rabi frequency (Ω), i.e., |Δ| ≫ Ω. Under these conditions, without Rydberg-Rydberg interactions (V ), further Rydberg excitation would be suppressed. However, the interaction between Rydberg atoms facilitates correlated excitations (resonant when V = Δ), enabling additional Rydberg atoms to be excited (Fig. 1(b)).
Figure 2: Our excitation transport scheme. (a) The van der Waals interaction shifts the two-excitation state |11〉, with the interaction strength Vri depending on the interatomic distance ri for i = 1, 2. To resonantly excite the second Rydberg excitation, the detuning relative to the |0〉↔|1〉 transition frequency is Δi = Vri . (b) A Rydberg excitation (blue sphere) can be driven toward the left (right) by applying sequential π pulses with alternating detunings starting from Δ2 (Δ1). The corresponding pulse sequences for leftward (rightward) transport are shown in (c) as solid blue (dashed orange) lines.
Our protocol can be extended to 2D networks with multiple excitations, potentially offering new avenues for quantum information processing.
Page updated
Google Sites
Report abuse