Neutal Atom Quantum Hardware

Last updated: June 22, 2023

Table of contents

Hardware Feature
Reference

Hardware Feature

A good summary of hardware details can be found here [1].

Coherence time. According to [2], the latest NA device coherence time can be up to 40 seconds.

Atom Spacing. The intersite spacing in neutral-atom trap arrays is typically 2–5 $\mu m$ [3].

Rydberg interaction constant. Depends on the particular Rydberg state used. For Bloqade [4], the default $C_6 = 862690 \times 2\pi$ MHz$\mu m^6$ for $|r \rangle = \vert 70S_{1/2} \rangle$ of the $^{87}$Rb atoms.

Rabi frequency $\Omega$ between $\vert 1 \rangle$ and $\vert r \rangle$. $\Omega \approx 2\pi\times 3.5$ MHz [5].

Rabi frequency $\Omega_{01}$ between $\vert 0 \rangle$ and $\vert 1 \rangle$. $\Omega_{01} \approx 2\pi\times 0.25$ MHz [5].

Bloackade Radius. The typical blockade radius is $8 \mu m \approx \sqrt[6]{C_6/\Omega}$.

1q gate. Fidelity: 99.9%. Latency: $\pi/\Omega =4\mu$s. ($2\pi$ means $\vert 0 \rangle\to \vert 1 \rangle \to \vert 0 \rangle$).

CZ gate. Fidelity: 97.4%. Latency: $2.732\pi/\Omega =0.39\mu$s [5]. $4\pi/\Omega =0.57\mu$s [6] and [7] Figure B1.1.

Readout. Fidelity: $\ge 0.95$. Latency: 10ms (fluorescence imaging). [1].

Atom Movement. According to [8], the relation between movement time $t$ and travel distance $D$ is $t = T_0 \sqrt{D/D_0}$, where $T_0 = 300\mu s$ and $D_0 = 50\mu m$. Fidelity loss from several factors, e.g., atom loss and decoherence. If only consider decoherence, the fidelity of atom movement is about 99.999\%, close to the fidelity of a single-qubit gate.

Atom Rearrangement. Atoms are loaded into a 2D array of optical tweezer traps and rearranged into defect-free patterns by a second set of moving tweezers. It takes a long time whose success rate is about 75%. Latency: 400 ms [1].

Control feature. With individual qubit control or with shared qubit control. Shared detuning $\Delta$? Shared rabi oscillator $\Omega$?

Measurement feature. Mid-circuit measurement: [9][10][11]. Support independent measurement on individual qubits? It is taking camera, it would become difficult to measurement one qubit individually.

Gate development timeline. [6] $\to$ [5] $\to$ [12] $\to$ [13]

Hamiltonian Feature. Quantum Hamiltonians encode the essential physical properties of a quantum system. For the analog mode of neutral-atom quantum computers, the quantum dynamics is governed by the Rydberg Hamiltonian $\hat{\mathcal{H}}$:

$$ i \hbar \dfrac{\partial}{\partial t} | \psi \rangle = \hat{\mathcal{H}}(t) | \psi \rangle, \frac{\mathcal{H}(t)}{\hbar} = \sum_j \frac{\Omega_j(t)}{2} \left( e^{i \phi_j(t) } | g_j \rangle \langle r_j | + e^{-i \phi_j(t) } | r_j \rangle \langle g_j | \right) - \sum_j \Delta_j(t) \hat{n}_j + \sum_{j < k} V_{jk} \hat{n}_j \hat{n}_k, $$

where $\Omega_j$, $\phi_j$, and $\Delta_j$ denote the Rabi frequency, laser phase, and the detuning of the driving laser field on atom (qubit) $j$ coupling the two states $| g_j \rangle$ (ground state) and $| r_j \rangle$ (Rydberg state); $\hat{n}_j = |r_j\rangle \langle r_j|$ is the number operator, and $V_{jk} = C_6/|\mathbf{x}_j - \mathbf{x}_k|^6$ describes the Rydberg interaction (van der Waals interaction) between atoms $j$ and $k$ where $\mathbf{x}_j$ denotes the position of the atom $j$; $C_6$ is the Rydberg interaction constant that depends on the particular Rydberg state used. For Bloqade [4], the default $C_6 = 862690 \times 2\pi$ MHZ $\mu m^6$ for $|r \rangle = \vert 70S_{1/2} \rangle$ of the $^{87}$Rb atoms; $\hbar$ is the reduced Planck's constant.

One can use the Rydberg Hamiltonian to understand the ground state properties of the corresponding system and to generate interesting quantum dynamics. The Rydberg Hamiltonian is generally specified by atom positions $\mathbf{x}_j$, Rabi frequencies $\Omega_j$, laser phase $\phi_j$, and detunings $\Delta_j$. In Bloqade, we can easily create a Hamiltonian by inputting these variable parameters into the function rydberg_h. Furthermore, by inputting waveforms for the Rabi frequency and detuning, we can easily generate time-dependent Hamiltonians.

Reference

[1] Karen Wintersperger, Florian Dommert, Thomas Ehmer, Andrey Hoursanov, Johannes Klepsch, Wolfgang Mauerer, Georg Reuber, Thomas Strohm, Ming Yin, and Sebastian Luber. Neutral atom quantum computing hardware: Performance and end-user perspective, 2023.

[2] Quantum Computing with Neutral Atoms — quantumtech.blog. https://quantumtech.blog/2023/01/17/quantum-computing-with-neutral-atoms/. [Accessed 01-May-2023].

[3] David S. Weiss and Mark Saffman. Quantum computing with neutral atoms. Physics Today, 70(7):44–50, 07 2017.

[4] Bloqade.jl: Package for the quantum computation and quantum simulation based on the neutral-atom architecture., 2023.

[5] Harry Levine, Alexander Keesling, Giulia Semeghini, Ahmed Omran, Tout T Wang, Sepehr Ebadi, Hannes Bernien, Markus Greiner, Vladan Vuletić, Hannes Pichler, et al. Parallel implementation of high-fidelity multiqubit gates with neutral atoms. Physical review letters, 123(17):170503, 2019.

[6] Dieter Jaksch, Juan Ignacio Cirac, Peter Zoller, Steve L Rolston, Robin Côté, and Mikhail D Lukin. Fast quantum gates for neutral atoms. Physical Review Letters, 85(10):2208, 2000.

[7] Loïc Henriet, Lucas Beguin, Adrien Signoles, Thierry Lahaye, Antoine Browaeys, Georges-Olivier Reymond, and Christophe Jurczak. Quantum computing with neutral atoms. Quantum, 4:327, 2020.

[8] Dolev Bluvstein, Harry Levine, Giulia Semeghini, Tout T Wang, Sepehr Ebadi, Marcin Kalinowski, Alexander Keesling, Nishad Maskara, Hannes Pichler, Markus Greiner, et al. A quantum processor based on coherent transport of entangled atom arrays. Nature, 604(7906):451–456, 2022.

[9] Felipe Giraldo Mejia, Aishwarya Kumar, Tsung-Yao Wu, Peng Du, and David S. Weiss. State-selective eit for quantum error correction in neutral atom quantum computers, 2022.

[10] Emma Deist, Yue-Hui Lu, Jacquelyn Ho, Mary Kate Pasha, Johannes Zeiher, Zhenjie Yan, and Dan M. Stamper-Kurn. Mid-circuit cavity measurement in a neutral atom array. Physical Review Letters, 129(20), nov 2022.

[11] T. M. Graham, L. Phuttitarn, R. Chinnarasu, Y. Song, C. Poole, K. Jooya, J. Scott, A. Scott, P. Eichler, and M. Saffman. Mid-circuit measurements on a neutral atom quantum processor, 2023.

[12] Sven Jandura and Guido Pupillo. Time-optimal two- and three-qubit gates for rydberg atoms. Quantum, 6:712, may 2022.

[13] Simon J. Evered, Dolev Bluvstein, Marcin Kalinowski, Sepehr Ebadi, Tom Manovitz, Hengyun Zhou, Sophie H. Li, Alexandra A. Geim, Tout T. Wang, Nishad Maskara, Harry Levine, Giulia Semeghini, Markus Greiner, Vladan Vuletic, and Mikhail D. Lukin. High-fidelity parallel entangling gates on a neutral atom quantum computer, 2023.

[14] David C. Spierings, Edwin Tham, Aharon Brodutch, and Ilia Khait. Preferred interaction ranges in neutral-atom arrays in the presence of noise, 2022.

[15] Jonathan M Baker, Andrew Litteken, Casey Duckering, Henry Hoffmann, Hannes Bernien, and Frederic T Chong. Exploiting long-distance interactions and tolerating atom loss in neutral atom quantum architectures. In 2021 ACM/IEEE 48th Annual International Symposium on Computer Architecture (ISCA), pages 818–831. IEEE, 2021.

[16] Andrew Litteken, Jonathan M. Baker, and Frederic T. Chong. Reducing runtime overhead via use-based migration in neutral atom quantum architectures, 2022.

[17] Bochen Tan, Dolev Bluvstein, Mikhail D. Lukin, and Jason Cong. Qubit mapping for reconfigurable atom arrays. In 2022 IEEE/ACM International Conference On Computer Aided Design (ICCAD), pages 1–9, 2022.

[18] Lea-Marina Steinert, Philip Osterholz, Robin Eberhard, Lorenzo Festa, Nikolaus Lorenz, Zaijun Chen, Arno Trautmann, and Christian Gross. Spatially tunable spin interactions in neutral atom arrays, 2022.

[19] Yuxiang Peng, Jacob Young, Pengyu Liu, and Xiaodi Wu. Simuq: A domain-specific language for quantum simulation with analog compilation, 2023.