# Project C5:

Micro ion traps (2005-2011)

## Summary

Summary This project aims to study the coupling of single ions or crystals of ions to mesoscopic solid state systems. The research is based on experimental techniques that have been successfully developed to control the quantum state of an ion crystal with high precision. Experiments concerning ion-based quantum computing have been following theoretical ideas proposed almost ten years ago. With the advent of micro- and nano-scale mechanical elements, the future challenge is the construction of microscopic ion trapping devices. The formation of metal-ceramic hybrid structures has been initiated recently while the suitability of semiconductor based micro-structures for trap electrodes still needs to be investigated. A final goal is to incorporate nano-structures into the design of quantum optical devices. The planned experiments will allow the study of exemplary interface between a well understood and well controlled quantum optical system - that is the single ion or a crystal of ions - and a mesoscopic, condensed matter object. Several lines of interest appear most appealing: 1) Systematic studies of the coupling between ions and neighboring surfaces at distances down to 100µm: A single ion used as a localized quantum probe for condensed matter and surface properties: The mutual coupling regards the motional degrees of freedom as well as the internal electronic states of the ion. Entangled states of two or more ions as decoherence-probe. Monitoring the overall quantum state evolution. The ion system is observed by means of laser spectroscopy in combination with the electron shelving technique; the evolution can be experimentally accessed and compared to theoretical calculations. The questions addressed are of importance from a fundamental point of view but may also have large impact on applications in quantum information technology. 2) A principal experimental challenge is the integration of micro- and nano-structures into ion trap technology. We will construct a linear arrangement of segmented ion traps, with decreasing size, such that the ions may initially be loaded into a standard ion trap with a dimension of a few 100µm and then subsequently transferred into smaller and smaller structures. With trap dimensions significantly below 100µm the ion's motional frequency may reach the GHz range. Similarly, since the trap electrodes are approaching mesoscopic dimensions, their vibrational eigen-frequencies are expected in the GHz frequency range. Their electrical and mechanical properties are to be described quantum mechanically. Coupling between the ion motion - controlled and monitored by laser-ion interaction - and the vibrational degrees of freedom of mechanical trap eigen-modes. Investigation of potentially novel features of coupling and decoherence: The interaction strength is varied by shifting the ion position with respect to the mesoscopic system. Note that the ion wave function is localized to a few nm and that its position is under full experimental control. 3) Linear ion crystals are suited for the simulation of quantum spin systems such as the Heisenberg- or the Ising-interaction. In this analog quantum simulator magnetic phase transitions may be observed allowing unprecedented opportunities for the measurement and manipulation of individual spins, while the strength and range of the interactions is varied.

## Project leaders

Prof. Dr. Ferdinand Schmidt-Kaler, Quanten-, Atom- und Neutronenphysik (QUANTUM), Institut für Physik, Universität Mainz

## Refs & Publications

F. Schmidt-Kaler and R. Gerritsma*"Entangled states of trapped ions allow measuring the magnetic field gradient produced by a single atomic spin"*

*EPL*

**99**, 53001 (2012)*;*doi: 10.1209/0295-5075/99/53001

A. Walther, F. Ziesel, T. Ruster, S. T. Dawkins, K. Ott, M. Hettrich, K. Singer, F. Schmidt-Kaler, and U. G. Poschinger

*"Controlling fast transport of cold trapped ions"*

*Phys. Rev. Lett.*

**109**, 080501 (2012)*;*doi: 10.1103/PhysRevLett.109.080501

R. Gerritsma, A. Negretti, H. Doerk, Z. Idziaszek, T. Calarco, and F. Schmidt-Kaler

*"Bosonic Josephson Junction Controlled by a Single Trapped Ion"*

*Phys. Rev. Lett.*

**109**, 080402 (2012)*;*doi: 10.1103/PhysRevLett.109.080402

O. Abah, J. Roßnagel, G. Jacob, S. Deffner, F. Schmidt-Kaler, K. Singer, and E. Lutz

*"Single ion heat engine with maximum efficiency at maximum power"*

*Phys. Rev. Lett.*

**109**, 203006 (2012)*;*doi: 10.1103/PhysRevLett.109.203006

U. G. Poschinger, A. Walther, M. Hettrich, F. Ziesel, and F. Schmidt-Kaler

*"Interaction of a laser with a qubit in thermal motion and its application to robust and efficient readout"*

*Appl. Phys. B*

**107**, 1159 (2012)*;*doi: 10.1007/s00340-012-4882-3

A. Walther, U. G. Poschinger, K. Singer, and F. Schmidt-Kaler

*"Precision measurements in ion traps using slowly moving standing waves"*

*Appl. Phys. B*

**107**, 1061 (2012)*;*doi: 10.1007/s00340-011-4740-8

U. Poschinger, A. Walther, K. Singer, and F. Schmidt-Kaler,

*"Observing the phase space trajectory of an entangled matter wave packet"*

*Phys. Rev. Lett.*

**105**, 263602 (2010)*;*doi: 10.1103/PhysRevLett.105.263602

P. Ivanov, U. Poschinger, K. Singer, and F. Schmidt-Kaler

*"Quantum gate in the decoherence-free subspace of trapped-ion qubits"*

*EPL*

**92**, 30006 (2010)*;*doi: 10.1209/0295-5075/92/30006

K. Singer, U. Poschinger, M. Murphy, P. Ivanov, F. Ziesel, T. Calarco, and F. Schmidt-Kaler

*"Colloquium: Trapped ions as quantum bits: Essential numerical tools"*

*Rev. Mod. Phys.*

**82**, 2609 (2010)*;*doi: 10.1103/RevModPhys.82.2609

G. Huber, F. Ziesel, U. Poschinger, K. Singer, and F. Schmidt-Kaler

*"A trapped-ion local field probe"*

*Appl. Phys. B*;

**100**, 725–730 (2010)

**10<**

W. Schnitzler, G. Jacob, R. Fickler, F. Schmidt-Kaler, and K. Singer

M. Hellwig, A. Bautista-Salvador, K. Singer, G. Werth, and F. Schmidt-Kaler

J. Eble, S. Ulm, P. Zahariev, F. Schmidt-Kaler, and K. Singer

I. Marzoli, P. Tombesi, G. Ciaramicoli, G. Werth, P. Bushev, S. Stahl, F. Schmidt-Kaler, M. Hellwig, C. Henkel, G. Marx, I. Jex, E. Stachowska, G. Szawiola, and A. Walaszyk

U. G. Poschinger, G. Huber, F. Ziesel, M. Deiß, M. Hettrich, S. A. Schulz, K. Singer, G. Poulsen, M. Drewsen, R. J. Hendricks, and F. Schmidt-Kaler

R. Fickler, W. Schnitzler, Norbert M. Linke, F. Schmidt-Kaler, and K. Singer

W. Schnitzler, N. M. Linke, R. Fickler, J. Meijer, F. Schmidt-Kaler, and K. Singer

M. Murphy, L. Jiang, N. Khaneja, and T. Calarco

P. Bushev, S. Stahl, R. Natali, G. Marx, E. Stachowska, G. Werth, M. Hellwig, and F. Schmidt-Kaler

G. Huber, F. Schmidt-Kaler, S. Deffner, and E. Lutz

S. Schulz, U. Poschinger, F. Ziesel, and F. Schmidt-Kaler

G. Huber, T. Deuschle, W. Schnitzler, R. Reichle, K. Singer, and F. Schmidt-Kaler

M. Schulz, H. Crepaz, F. Schmidt-Kaler, J. Eschner, and R. Blatt

Chr. Wunderlich, Th. Hannemann, T. Koerber, H. Haeffner, Ch. Roos, W. Haensel, R. Blatt, and F. Schmidt-Kaler

J.F. Eble and F. Schmidt-Kaler

F. Schmidt-Kaler

*;*doi: 10.1007/s00340-010-4148-xW. Schnitzler, G. Jacob, R. Fickler, F. Schmidt-Kaler, and K. Singer

*"Focusing a deterministic single-ion beam"**New J. Phys.***12**, 065023 (2010)M. Hellwig, A. Bautista-Salvador, K. Singer, G. Werth, and F. Schmidt-Kaler

*"Fabrication of a segmented micro Penning trap and numerical investigations of versatile ion positioning protocols"**New J. Phys.***12**, 065019 (2010)J. Eble, S. Ulm, P. Zahariev, F. Schmidt-Kaler, and K. Singer

*"Feedback-optimized operations with linear ion crystals"**J. Opt. Soc. Am. B***27**, A99-A104 (2010)I. Marzoli, P. Tombesi, G. Ciaramicoli, G. Werth, P. Bushev, S. Stahl, F. Schmidt-Kaler, M. Hellwig, C. Henkel, G. Marx, I. Jex, E. Stachowska, G. Szawiola, and A. Walaszyk

*"Experimental and theoretical challenges for the trapped electron quantum computer"**J. Phys. B: At. Mol. Opt. Phys.***42**, 154010 (2009)U. G. Poschinger, G. Huber, F. Ziesel, M. Deiß, M. Hettrich, S. A. Schulz, K. Singer, G. Poulsen, M. Drewsen, R. J. Hendricks, and F. Schmidt-Kaler

*"Coherent manipulation of a 40Ca+ spin qubit in a micro ion trap"**J. Phys. B: At. Mol. Opt. Phys.***42**, 154013 (2009)R. Fickler, W. Schnitzler, Norbert M. Linke, F. Schmidt-Kaler, and K. Singer

*"Optimized focusing ion optics for an ultracold deterministic single ion source targeting nm resolution"**Journal of Modern Optics***56**, 2061 (2009)W. Schnitzler, N. M. Linke, R. Fickler, J. Meijer, F. Schmidt-Kaler, and K. Singer

*"Deterministic Ultracold Ion Source Targeting the Heisenberg Limit"**Phys. Rev. Lett.***102**, 070501 (2009)M. Murphy, L. Jiang, N. Khaneja, and T. Calarco

*"High-fidelity fast quantum transport with imperfect controls"**Phys. Rev. A***79**, 020301R (2009)P. Bushev, S. Stahl, R. Natali, G. Marx, E. Stachowska, G. Werth, M. Hellwig, and F. Schmidt-Kaler

*"Electrons in a cryogenic planar Penning trap and experimental challenges for quantum processing"**Eur. Phys. J. D***50**, 97–102 (2008)G. Huber, F. Schmidt-Kaler, S. Deffner, and E. Lutz

*"Employing trapped cold ions to verify the quantum Jarzynski equality"**Phys. Rev. Lett.***101**, 070403 (2008)S. Schulz, U. Poschinger, F. Ziesel, and F. Schmidt-Kaler

*"Sideband cooling and coherent dynamics in a microchip multi-segmented ion trap"**New J. Phys.***10**, 045007 (2008)G. Huber, T. Deuschle, W. Schnitzler, R. Reichle, K. Singer, and F. Schmidt-Kaler

*"Transport of ions in a segmented linear Paul trap in printed-circuit-board technology"**New J. Phys.***10**, 013004 (2008)M. Schulz, H. Crepaz, F. Schmidt-Kaler, J. Eschner, and R. Blatt

*"Transfer of trapped atoms between two optical tweezer potentials"**Journal of Modern Optics***54**, Issue 11, 1619-1626 (2007)Chr. Wunderlich, Th. Hannemann, T. Koerber, H. Haeffner, Ch. Roos, W. Haensel, R. Blatt, and F. Schmidt-Kaler

*"Robust state preparation of a single trapped ion by adiabatic passage"**Journal of Modern Optics***54**, Issue 11, 1541-1549 (2007)J.F. Eble and F. Schmidt-Kaler

*"Optimization of frequency modulation transfer spectroscopy on the calcium 41 S0 to 41 P1 transition"**Applied Physics B: Lasers and Optics,***88**, Number 4 (2007 )F. Schmidt-Kaler

*"Quantum Computing with Cold Ions and Atoms: Experiments with Ion Traps"**Lectures on Quantum Information, Wiley-VCH, Berlin, ISBN-13: 978-3-527-40527-5, Chapter 6. Quantu*

S. Schulz, U. Poschinger, K. Singer, and F. Schmidt-Kaler

R. Reichle, D. Leibfried, R. B. Blakestad, J. Britton, J. D. Jost, E.Knill, C. Langer, R. Ozeri, S. Seidelin, and D. J. Wineland

H. Häffner, F. Schmidt-Kaler, C.F. Roos, T., Körber, M. Chwalla, M. Riebe, J. Benhelm, U. D. Rapol, C. Becher, and R. Blatt

S. Schulz, U. Poschinger, K. Singer, and F. Schmidt-Kaler

*"Optimization of segmented linear Paul traps and transport of stored particles"**Progress of Physics, Wiley***54**, No. 8 - 10, 648 (2006)R. Reichle, D. Leibfried, R. B. Blakestad, J. Britton, J. D. Jost, E.Knill, C. Langer, R. Ozeri, S. Seidelin, and D. J. Wineland

*"Transport dynamics of single ions in segmented microstructured Paul trap arrays"**Progress of Physics, Wiley***54**, No. 8 - 10, 666 (2006)H. Häffner, F. Schmidt-Kaler, C.F. Roos, T., Körber, M. Chwalla, M. Riebe, J. Benhelm, U. D. Rapol, C. Becher, and R. Blatt

*"Robust Entanglement"**Appl. Phys. B,***81**, No. 2-3 (2005)