Coherent manipulation of a<sup>40</sup>Ca<sup>+</sup>spin qubit in a micro ion trap

Poschinger, Ulrich; Huber, G.; Ziesel, Frank; Deiß, Markus; Hettrich, M.; Schulz, Stephan; Singer, Kilian; Poulsen, Gregers; Drewsen, Michael; Hendricks, Richard; Schmidt‐Kaler, F.

doi:10.1088/0953-4075/42/15/154013

Cited by 50 publications

(58 citation statements)

References 38 publications

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“…The ion used for the experiments is 40 Ca + , where an external magnetic field splits the S 1/2 ground state into two levels, m J = ±1/2, henceforth referred to as |↑ and |↓ . Qubit rotations between these levels are mediated by stimulated Raman transitions [15,16]. Each experimental run is started by i) Doppler cooling and followed by ii) optical pumping, leaving the ion in the |↑ state.…”

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confidence: 99%

“…v) For determining the motional state, stimulated Raman transitions between |↑ and |↓ are driven by a pair of off-resonant beams propagating at 90 • with respect to each other. The effective wavevector of the beams is aligned along the trap axis, providing a coupling to the axial mode of vibration, characterized by a Lamb-Dicke factor of η ≈ 0.23. vi) Spin read-out is performed by a shelving pulse followed by the detection of state-dependent fluorescence [15].…”

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confidence: 99%

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Controlling Fast Transport of Cold Trapped Ions

et al. 2012

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We realize fast transport of ions in a segmented micro-structured Paul trap. The ion is shuttled over a distance of more than 10 4 times its groundstate wavefunction size during only 5 motional cycles of the trap (280 µm in 3.6 µs). Starting from a ground-state-cooled ion, we find an optimized transport such that the energy increase is as low as 0.10±0.01 motional quanta. In addition, we demonstrate that quantum information stored in a spin-motion entangled state is preserved throughout the transport. Shuttling operations are concatenated, as a proof-of-principle for the shuttling-based architecture to scalable ion trap quantum computing. . Scalable information processing in a multiplexed ion trap can be accomplished by having fixed processing sites where logic operations are performed, and ion qubits will be moved in and out of these regions by shuttling operations. The duration of such shuttling has to be much faster than the relevant decoherence times [4]. Furthermore, it is desirable to reduce the total time consumption of all relevant operations, where shuttling will contribute a considerable amount [5], and aim for the performance of the naturally fast solid state architectures [6]. So far, ion shuttling in a multiplexed trap has been demonstrated together with additional sympathetic cooling [7], and in the adiabatic regime, where the transient displacement of the ion is smaller than the size of the its wavepacket [8,9]. Transport of neutral atoms have also been performed using magnetic [10] or optical [11] techniques.Because quantum gate operations require ions close to the motional ground state and fast transport inherently creates motional excitation, the challenge is to develop transport protocols that guarantee sufficiency small energy transfer. In this work we demonstrate shuttling operations that are highly non-adiabatic while the final state of the ion is close to the motional groundstate. We also show that quantum information stored in both the motional and the spin degree of freedom is preserved through the shuttling.During a shuttling operation, the ion motion in the harmonic trapping potential is excited when the acceleration is sufficiently strong. This motional excitation is a harmonic oscillation, characterized by a well defined phase, thus allowing it to be canceled out by proper management of the forces involved during or after the transport. We experimentally demonstrate two methods of canceling the acquired motional excitation. One method uses two shuttles, where the transport to the destination generates the same net momentum transfer as the transport back, but is applied 180 • out of phase with respect to the secular oscillation of the ion (Fig. 1b). We refer to this as the pairwise energy-neutral transport. For the second scheme, the self-neutral transport we apply a sharp counter-"kick" to the ion at the end of a single transport operation, stopping its motion (Fig. 1c). This case of single-sided transport allows even faster shuttling and can be sequentially repeated since it is ener...

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Controlling Fast Transport of Cold Trapped Ions

et al. 2012

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“…1. As the method is based on the discrete discrimination of atomic states of a single trapped particle [17,18], it is robust against many systematic error sources which affect other existing methods.The off-resonant laser is characterized by its detuning ∆ from the 4 2 S 1/2 ↔ 4 2 P 1/2 transition, the Rabi frequency Ω and the relative amplitudes q , which characarXiv:1505.02574v3 [quant-ph] 9 Oct 2015 2 terize the circular (q = ±1, denoted '±' henceforth) and π (q = 0) polarization components.The dispersive interaction with the laser field, detuned by a frequency ∆ from resonance, causes ac Stark shifts [19,20] of the energy levels. Specifically, we are interested in the differential ac Stark shift ∆ S between the two Zeeman-sublevels of the electronic ground state |S 1/2 , m S = ±1/2 , denoted henceforth as |↑ and |↓ .…”

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“…Now, the ion is illuminated with light near 397 nm, detuned by ∆ from the 4 2 S 1/2 ↔ 4 2 P 1/2 transition to induce both the dispersive and absorptive interactions, which allow for determining ∆ S and R ± . Spin read-out is accomplished by shelving population from the |↑ level to the metastable 3 2 D 5/2 state by means of rapid adiabatic passage (RAP) pulses [18,25]. This allows for discrimination between |↑ and |↓ as the linewidth of the 4 2 S 1/2 ↔ 3 2 D 5/2 quadrupole transition and the bandwidth of the RAP pulses are much smaller than the Zeeman splitting.…”

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Measurement of Dipole Matrix Elements with a Single Trapped Ion

et al. 2015

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We demonstrate a method to determine dipole matrix elements by comparing measurements of dispersive and absorptive light ion interactions. We measure the matrix element pertaining to the Ca II H line, i.e. the 4 2 S 1/2 ↔ 4 2 P 1/2 transition of 40 Ca + , for which we find the value 2.8928(43) ea0.Moreover, the method allows us to deduce the lifetime of the 4 2 P 1/2 state to be 6.904(26) ns, which is in agreement with predictions from recent theoretical calculations and resolves a longstanding discrepancy between calculated values and experimental results.PACS numbers: 37.10. Ty, 32.80.Qk, 03.67.Lx Methods for trapping and cooling single or few atoms, molecules or ions and manipulating them at the quantum level have opened up new avenues for precision laser spectroscopy. In particular, quantum logic techniques [1] have enabled a new accuracy regime of timekeeping with optical atomic clocks [2]. In contrast to atomic transition frequencies, dipole matrix elements and radiative lifetimes are still notoriously hard to determine at high accuracy, but are important for the quantification of black body radiation shifts of atomic clocks [3], interpretation of astrophysical spectra [4,5], novel approaches for the search for physics beyond standard model [6,7] and for testing the accuracy of atomic structure calculations [8].Regarding measurements of radiative lifetimes and transition matrix elements, established methods e.g. based on ion beams have been successfully complemented by novel techniques based on trapped particles. For 87 Rb, dipole matrix elements have been determined on the 10 −3 uncertainty level by diffraction in a condensate [9], while for the 6p 2 P o 1/2 state of 174 Yb + , the radiative lifetime has been measured by time-resolved counting of photons emitted from a single trapped ion [10]. A related technique was used for neutral 171 Yb in an optical lattice [11].The species Ca + is widely used in quantum optics experiments, and its II H line led to the discovery of the interstellar medium [12]. For 40 Ca + , branching ratios between different decay channels have been determined at uncertainties approaching the 10 −5 level [13,14], and lifetimes of metastable states have been accurately measured [15]. The radiative lifetime of the 4 2 P 1/2 excited state of 40 In this work, we determine the radiative decay rates and the lifetime of the 4 2 P 1/2 excited state of 40 Ca + together with the dipole matrix element of the 4 2 S 1/2 ↔ 4 2 P 1/2 transition. The cornerstone of our scheme is the comparison between the dispersive and absorptive interactions, which occur upon driving this transition with an off-resonant laser, see Fig. 1. As the method is based on the discrete discrimination of atomic states of a single trapped particle [17,18], it is robust against many systematic error sources which affect other existing methods.The off-resonant laser is characterized by its detuning ∆ from the 4 2 S 1/2 ↔ 4 2 P 1/2 transition, the Rabi frequency Ω and the relative amplitudes q , which characarXiv:1505.025...

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“…The measured output voltage noise at the trap frequency, in the steady state, is as low as 1.0·10 −9 V/ √ Hz. This results in a spectral density of the electric field noise of about 3.6·10 −13 V 2 / Hz m 2 , which in turn yields a heating rate that lower than the actually observed heating rate ofṅ ≈ 0.3 ms −1 [24] by one order of magnitude; it therefore does not significantly contribute to the anomalous heating. Care was take to suppress digital noise, i.e.…”

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confidence: 82%

Experimental creation and analysis of displaced number states

Ziesel¹,

Ruster²,

Walther³

et al. 2013

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. We create displaced number states, which are non-classical generalizations of coherent states, of a vibrational mode of a single trapped ion. The creation of these states is accomplished by a combination of optical and electrical manipulation of the ion. A number state is first prepared by laser-driven climbing of the Jaynes-Cummings ladder, followed by displacement created by a sudden shift of the electrostatic trapping potential. Number states n =0,1 and 2 are prepared, and displacement amplitudes of up to α ≈ 2.8 are reached. The states are analyzed tomographically, and we find a good agreement with the theoretically expected results for displaced number states. Quantum features elucidating the concept of interference in phase space are clearly demonstrated experimentally.

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Coherent manipulation of a⁴⁰Ca⁺spin qubit in a micro ion trap

Cited by 50 publications

References 38 publications

Controlling Fast Transport of Cold Trapped Ions

Controlling Fast Transport of Cold Trapped Ions

Measurement of Dipole Matrix Elements with a Single Trapped Ion

Experimental creation and analysis of displaced number states

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Coherent manipulation of a40Ca+spin qubit in a micro ion trap

Cited by 50 publications

References 38 publications

Controlling Fast Transport of Cold Trapped Ions

Controlling Fast Transport of Cold Trapped Ions

Measurement of Dipole Matrix Elements with a Single Trapped Ion

Experimental creation and analysis of displaced number states

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Coherent manipulation of a⁴⁰Ca⁺spin qubit in a micro ion trap