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Title:   Quantum information technologies and entanglement with trapped ions

Speaker:  Ferdinand Schmidt-Kaler, QUANTUM, Univ. Mainz  (

Date: 08/02/22


Quantum technologies allow for fully novel schemes of computing, simulation and sensing. For quantum computing, we employ trapped ions in modern segmented ion traps as scalable and freely reconfigurable qubit register [1]. I will give an overview of the recent progress, where gate fidelities of 99.995% (single bit) and 99.6% (two bit) are reached. This includes a discussion of different architectures, the required trap technologies and fabrication methods, control electronics for quantum register reconfigurations, and recent improvements of qubit coherence and gate performance. Using a segmented micro-ion trap for implementing a reconfigurable qubit register we have realized multi-qubit entanglement [2]. Topological quantum error correction [3] is a current aim to leave the NISQ area of quantum computing.
Also, I describe our long-distance ion transports, thus realizing a deterministic ion source, which allows for delivering Ca+ ions on demand and focus it into a spot of a few nm [5]. The source can be operated also with any additional second ion, co-trapped and sympathetically cooled together with Ca+ and eventually extracted [6]. Recently, we have implemented a deterministic ion fountain where a single ion is recaptured after a flight outside the trap [8], long-term goal is a Stern Gerlach beam splitter or spin-dependent interferometer [7].

[1] Blatt, Wineland, Nat. 453, 1008 (2008), Kielpinski, Wineland, Nat. 417, 709 (2002),
Schindler et al, NJP 15, 123012 (2013), Friis et al, Phys. Rev. X 8, 021012 (2018),
Debenath et al, Nat. 536, 63 (2016), Kaushal, et al, AVS Quantum Sci. 2, 014101 (2020)
[2] Kaufmann er al, Phys. Rev. Lett.  119, 150503 (2017)
[3] Bermudez, et al, Phys. Rev. X 7, 041061 (2017), J.Hilder, et al., Fault-tolerant parity readout on a shuttling-based trapped-ion quantum computer, Phys. Rev. X. (2022) arXiv:2102.12047
[4] Vogel et al, Phys. Rev. Lett. 123, 153603 (2019)
[5] Jacob et  al, Phys. Rev. Lett. 117, 043001 (2016)
[6] Groot-Berning, et al, arXiv:2101.01979 , Phys. Rev. A 99, 023420 (2019), Groot-Berning, et al, Phys. Rev. Lett.123, 106802 (2019)
[7] Stopp et al, arXiv:2108.06948, Henkel et al., New Jour. of Phys. 21, 083022 (2019)

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