Nano Beams and Quantum Computing Infrastructure

Precision beam control for near-future chips and far-future computers

Example of the work toward a technological basis for quantum computing: deposition and spatially resolved, in situ monitoring of a single atom.`

Ion implantation and nanofabrication are exciting areas of research that are particularly applicable to quantum computing. A joint UC Berkeley, LBNL, and Princeton effort is in place to develop the theory, fabrication, and measurement aspects of a silicon-based ("Kane") approach to quantum computing. The monitored implantation, to nanometer accuracy, of a single ion has been achieved in the effort to implement a qubit array. These efforts are supported by the National Security Agency, which has a strong interest in the long-term potential of such machines. Though quantum computing is considered to be years away from application, it has truly revolutionary potential, especially in areas applicable to encryption. The IBT contribution is deeply infrastructural and oriented toward one possible pathway to quantum computing hardware: the use of electron spins of donor atoms in silicon as qubits.

Collaborators from IBT, UC Berkeley, and Princeton University are working on all aspects of device fabrication, coherence theory, and spin measurements, all of which are key items in a quantum computing toolkit. The work at LBNL takes three converging paths:

Development of a single ion placement technique, based on the integration of a scanning force microscope with ion beams.
Development of single spin readout transistors, based on spin-dependent transport in accumulation mode field effect transistors (aFETs).
Optimization of processing steps for retention of long coherence times of donor spins integrated in device structures. Nuclear spin coherence times greater than 1 second have been demonstrated.

A collaboration with the University of California, Santa Barbara is also in place to develop a non-silicon approach to quantum computing gates, based on nitrogen-vacancy (NV) defects in the crystal structure of diamond. This approach also uses qubits based on a single atom, thus its special appropriateness to this program.

Relevant publications:

(click on the years to see the publications) show all hide all

2013

C.D. Weis and T.Schenkel Solid-state physics: Single spins in silicon see the light Nature 497 46--47 (2013) doi journal web page bibtex
@article{ Weis:Nature-497-46,
doi = "10.1038/497046a",
author = "C.D. Weis and T.Schenkel",
title = "Solid-state physics: Single spins in silicon see the light",
url = "http://www.nature.com/nature/journal/v497/n7447/full/497046a.html",
journal = "Nature",
year = "2013",
volume = "497",
pages = "46--47"
}

2010

DavidM. Toyli, ChristophD. Weis, GregoryD. Fuchs, Thomas Schenkel and DavidD. Awschalom Chip-Scale Nanofabrication of Single Spins and Spin Arrays in Diamond Nano Lett. 10(8) 3168--3172 (2010) doi bibtex
@article{ Toyli:NL-10-3168,
doi = "10.1021/nl102066q",
author = "DavidM. Toyli and ChristophD. Weis and GregoryD. Fuchs and Thomas Schenkel and DavidD. Awschalom",
title = "Chip-Scale Nanofabrication of Single Spins and Spin Arrays in Diamond",
journal = "Nano Lett.",
year = "2010",
number = "8",
pages = "3168--3172",
volume = "10",
abstract = "We demonstrate a technique to nanofabricate nitrogen vacancy (NV) centers in diamond based on broad-beam nitrogen implantation through apertures in electron beam lithography resist. This method enables high-throughput nanofabrication of single NV centers on sub-100-nm length scales. Secondary ion mass spectroscopy measurements facilitate depth profiling of the implanted nitrogen to provide three-dimensional characterization of the NV center spatial distribution. Measurements of NV center coherence with on-chip coplanar waveguides suggest a pathway for incorporating this scalable nanofabrication technique in future quantum applications."
}
G.D. Fuchs, V.V. Dobrovitski, D.M. Toyli, F.J. Heremans, C.D. Weis, Thomas Schenkel and D.D. Awschalom Excited-state spin coherence of a single nitrogen-vacancy centre in diamond Nature Physics 6(9) 668--672 (2010) doi bibtex
@article{ Fuchs:NP-9-668,
doi = "10.1038/NPHYS1716",
author = "G.D. Fuchs and V.V. Dobrovitski and D.M. Toyli and F.J. Heremans and C.D. Weis and Thomas Schenkel and D.D. Awschalom",
title = "Excited-state spin coherence of a single nitrogen-vacancy centre in diamond",
journal = "Nature Physics",
year = "2010",
number = "9",
pages = "668--672",
volume = "6",
abstract = "Nitrogen-vacancy centres in diamond are a solid-state analogue of trapped atoms, with fine structure in both the ground and excited states that may be used for advanced quantum control. These centres are promising candidates for spin-based quantum information processing1-3 and magnetometry4-6 at room temperature. Knowledge of the excited-state (ES) structure and coherence is critical to evaluating the ES as a room-temperature quantum resource, for example for a fast, optically gated swap operation with a nuclear-spin memory(7). Here we report experiments that probe the ES-spin coherence of single nitrogen-vacancy centres. Using a combination of pulsed-laser excitation and nanosecond-scale microwave manipulation, we observed ES Rabi oscillations, and multipulse resonant control enabled us to study coherent ES electron/nuclear-spin interactions. To understand these processes, we developed a finite-temperature theory of ES spin dynamics that also provides a pathway towards engineering longer ES spin coherence."
}

2009

C.C. Lo, A.Persaud, S.Duhey, D.Olynick, F.Borondics, M.C. Martin, H.A. Bechtel, J.Bokor and T.Schenkel Device fabrication and transport measurements of FinFETs built with $^28$Si SOI wafers towards donor qubits in silicon Semiconductor Science and Technology 24(10) 105022 (2009) doi journal web page arXiv.org bibtex
@article{ Lo:SST-24-105022,
doi = "10.1088/0268-1242/24/10/105022",
author = "C.C. Lo and A.Persaud and S.Duhey and D.Olynick and F.Borondics and M.C. Martin and H.A. Bechtel and J.Bokor and T.Schenkel",
title = "Device fabrication and transport measurements of FinFETs built with $^28$Si SOI wafers towards donor qubits in silicon",
url = "http://stacks.iop.org/0268-1242/24/105022",
journal = "Semiconductor Science and Technology",
year = "2009",
number = "10",
volume = "24",
eprint = "arXiv:0906.1995v1 [cond-mat.mes-hall]",
pages = "105022"
}
T.Schenkel, C.C. Lo, C.D. Weis, A.Schuh, A.Persaud and J.Bokor Critical issues in the formation of quantum computer test structures by ion implantation Nuclear Instruments and Methods in Physics Research B 267(16) 2563--2566 (2009) doi arXiv.org bibtex
@article{ Schenkel:NIMB-267-2563,
doi = "10.1016/j.nimb.2009.05.061",
author = "T.Schenkel and C.C. Lo and C.D. Weis and A.Schuh and A.Persaud and J.Bokor",
title = "Critical issues in the formation of quantum computer test structures by ion implantation",
abstract = "The formation of quantum computer test structures in silicon by ion implantation enables the characterization of spin readout mechanisms with ensembles of dopant atoms and the development of single atom devices. We briefly review recent results in the characterization of spin dependent transport and single ion doping and then discuss the diffusion and segregation behaviour of phosphorus, antimony and bismuth ions from low fluence, low energy implantations as characterized through depth profiling by secondary ion mass spectrometry (SIMS). Both phosphorus and bismuth are found to segregate to the SiO2/Si interface during activation anneals, while antimony diffusion is found to be minimal. An effect of the ion charge state on the range of antimony ions, Sb-121(25+), in SiO2/Si is also discussed. (C) 2009 Elsevier B. V. All rights reserved.",
year = "2009",
number = "16",
pages = "2563--2566",
volume = "267",
eprint = "arXiv:0904.4688v1 [cond-mat.mes-hall]",
journal = "Nuclear Instruments and Methods in Physics Research B"
}

2008

J.J.L. Morton, A.M. Tyryshkin, R.M. Brown, S.Shankar, B.W. Lovett, A.Ardavan, T.Schenkel, E.E. Haller, J.W. Ager and S.A. Lyon Solid-state quantum memory using the $^31$P nuclear spin Nature 455(23) 1085--1088 (2008) pdf bibtex
@article{ Morton:Nature-455-1085,
author = "J.J.L. Morton and A.M. Tyryshkin and R.M. Brown and S.Shankar and B.W. Lovett and A.Ardavan and T.Schenkel and E.E. Haller and J.W. Ager and S.A. Lyon",
title = "Solid-state quantum memory using the $^31$P nuclear spin",
journal = "Nature",
year = "2008",
volume = "455(23)",
pages = "1085--1088"
}
M.Sarovar, K.C. Young, T.Schenkel and K.B. Whaley Quantum nondemolition measurements of single donor spins in semiconductors Physical Review B 78 245302 (2008) pdf doi journal web page bibtex
@article{ Saraovar:PRB-78-245302,
doi = "10.1103/PhysRevB.78.245302",
author = "M.Sarovar and K.C. Young and T.Schenkel and K.B. Whaley",
title = "Quantum nondemolition measurements of single donor spins in semiconductors",
url = "http://link.aps.org/doi/10.1103/PhysRevB.78.245302",
journal = "Physical Review B",
year = "2008",
volume = "78",
pages = "245302"
}
C.D. Weis, A.Schuh, A.Batra, A.Persaud, I.W. Rangelow, J.Bokor, C.C. Lo, S.Cabrini, E.Sideras-Haddad, G.D. Fuchs, R.Hanson, D.D. Awschalom and T.Schenkel Single atom doping for quantum device development in diamond and silicon Journal of Vacuum Science and Technology B 26(6) 2596--2600 (2008) pdf doi bibtex
@article{ Weis:JVST-26-2596,
doi = "10.1116/1.2968614",
author = "C.D. Weis and A.Schuh and A.Batra and A.Persaud and I.W. Rangelow and J.Bokor and C.C. Lo and S.Cabrini and E.Sideras-Haddad and G.D. Fuchs and R.Hanson and D.D. Awschalom and T.Schenkel",
title = "Single atom doping for quantum device development in diamond and silicon",
abstract = "The ability to inject dopant atoms with high spatial resolution, flexibility in dopant species, and high single ion detection fidelity opens opportunities for the study of dopant fluctuation effects and the development of devices in which function is based on the manipulation of quantum states in single atoms, such as proposed quantum computers. The authors describe a single atom injector, in which the imaging and alignment capabilities of a scanning force microscope (SFM) are integrated with ion beams from a series of ion sources and with sensitive detection of current transients induced by incident ions. Ion beams are collimated by a small hole in the SFM tip and current changes induced by single ion impacts in transistor channels enable reliable detection of single ion hits. They discuss resolution limiting factors in ion placement and processing and paths to single atom (and color center) array formation for systematic testing of quantum computer architectures in silicon and diamond.",
year = "2008",
number = "6",
pages = "2596--2600",
volume = "26",
journal = "Journal of Vacuum Science and Technology B"
}

2007

A.Batra, C.D. Weis, J.Reijonen, A.Persaud, S.Cabrini, C.C. Lo, J.Bokor and T.Schenkel Detection of low energy single ion impacts in micron scale transistors at room temperature Applied Physics Letters 91(19) 193502 (2007) pdf doi bibtex
@article{ Batra:APL-91-193502,
doi = "10.1063/1.2805634",
author = "A.Batra and C.D. Weis and J.Reijonen and A.Persaud and S.Cabrini and C.C. Lo and J.Bokor and T.Schenkel",
title = "Detection of low energy single ion impacts in micron scale transistors at room temperature",
journal = "Applied Physics Letters",
year = "2007",
number = "19",
pages = "193502",
volume = "91",
abstract = "We report the detection of single ion impacts through monitoring of changes in the source-drain currents of field effect transistors at room temperature. Implant apertures are formed in the interlayer dielectrics and gate electrodes of planar, microscale transistors by electron beam assisted etching. Device currents increase due to the generation of positively charged defects in gate oxides when ions (Sb-121(12+,14+) and Xe6+; 50-70 keV) impinge into channel regions. Implant damage is repaired by rapid thermal annealing, enabling iterative cycles of device doping and electrical characterization for the development of single atom devices and studies of dopant fluctuation effects."
}
C.C. Lo, J.Bokor, T.Schenkel, A.M. Tyryshkin and S.A. Lyon Spin-Dependent Scattering off Neutral Antimony Donors in 28Si Field-Effect Transistors Applied Physics Letters 91 242106 (2007) bibtex
@article{ Lo:APL-91-242106,
author = "C.C. Lo and J.Bokor and T.Schenkel and A.M. Tyryshkin and S.A. Lyon",
title = "Spin-Dependent Scattering off Neutral Antimony Donors in 28Si Field-Effect Transistors",
journal = "Applied Physics Letters",
year = "2007",
volume = "91",
pages = "242106"
}

2006

F.R. Bradbury, A.M. Tyryshkin, G.Sabouret, J.Bokor, T.Schenkel and S.A. Lyon Stark Tuning of Donor Electron Spins in Silicon Physical Review Letters 97 176404 (2006) pdf doi journal web page arXiv.org bibtex
@article{ Bradbury:PRL-97-176404,
doi = "10.1103/PhysRevLett.97.176404",
author = "F.R. Bradbury and A.M. Tyryshkin and G.Sabouret and J.Bokor and T.Schenkel and S.A. Lyon",
title = "Stark Tuning of Donor Electron Spins in Silicon",
url = "http://link.aps.org/doi/10.1103/PhysRevLett.97.176404",
journal = "Physical Review Letters",
year = "2006",
volume = "97",
eprint = "cond-mat/0603324",
pages = "176404"
}
T.Schenkel, A.M. Tyryshkin, R.deSousa, K.B. Whaley, J.Bokor, J.A. Liddle, A.Persaud, J.Shangkuan, I.Chakarov and S.A. Lyon Electrical activation and spin coherence of ultra low dose antimony implants in silicon Applied Physics Letters 88(11) 112101 (2006) pdf arXiv.org bibtex
@article{ Schenkel:APL-88-112101,
author = "T.Schenkel and A.M. Tyryshkin and R.deSousa and K.B. Whaley and J.Bokor and J.A. Liddle and A.Persaud and J.Shangkuan and I.Chakarov and S.A. Lyon",
title = "Electrical activation and spin coherence of ultra low dose antimony implants in silicon",
journal = "Applied Physics Letters",
year = "2006",
number = "11",
volume = "88",
eprint = "cond-mat/0507318",
pages = "112101"
}
T.Schenkel, J.A. Liddle, J.Bokor, A.Persaud, S.J. Park, J.Shangkuan, C.C. Lo, S.Kwon, S.A. Lyon, A.M. Tyryshkin, I.W. Rangelow, Y.Sarov, D.H. Schneider, J.Ager and R.deSousa Strategies for integration of donor electron spin qubits Microelectronic Engineering 83(4--9) 1814--1817 (2006) pdf bibtex
@article{ Schenkel:ME-83-1814,
author = "T.Schenkel and J.A. Liddle and J.Bokor and A.Persaud and S.J. Park and J.Shangkuan and C.C. Lo and S.Kwon and S.A. Lyon and A.M. Tyryshkin and I.W. Rangelow and Y.Sarov and D.H. Schneider and J.Ager and R.deSousa",
title = "Strategies for integration of donor electron spin qubits",
journal = "Microelectronic Engineering",
year = "2006",
number = "4--9",
volume = "83",
pages = "1814--1817"
}
A.M. Tyryshkin, S.A. Lyon, T.Schenkel, J.Bokor, J.Chu, W.Jantasch, F.Schäffler, J.L. Truitt, S.N. Coppersmith and M.A. Eriksson Electron Spin Coherence in Silicon Physica E 35 257--263 (2006) pdf bibtex
@article{ Tyryshkin:PE-35-257,
author = "A.M. Tyryshkin and S.A. Lyon and T.Schenkel and J.Bokor and J.Chu and W.Jantasch and F.Schäffler and J.L. Truitt and S.N. Coppersmith and M.A. Eriksson",
title = "Electron Spin Coherence in Silicon",
journal = "Physica E",
year = "2006",
volume = "35",
pages = "257--263"
}

2004

S.J. Park, J.A. Liddle, A.Persaud, F.I. Allen, T.Schenkel and J.Bokor Formation fo 15 nm scale Coloumb blockade structures in silicon by electron beam lithography with a bilayer resist process Journal of Vacuum Science and Technology B 22(6) 3115--3118 (2004) pdf bibtex
@article{ Park:JVSTB-22-3115,
author = "S.J. Park and J.A. Liddle and A.Persaud and F.I. Allen and T.Schenkel and J.Bokor",
title = "Formation fo 15 nm scale Coloumb blockade structures in silicon by electron beam lithography with a bilayer resist process",
journal = "Journal of Vacuum Science and Technology B",
volume = "22(6)",
year = "2004",
pages = "3115--3118",
}
S.J. Park, A.Persaud, J.A. Liddle, J.Nilsson, J.Bokor, D.H. Schneider, I.W. Rangelow and T.Schenkel Processing issues in top-down approaches to quantum computer development in silicon Microelectronic Engineering 73--74 695--700 (2004) pdf arXiv.org bibtex
@article{ Park:ME-73-695,
author = "S.J. Park and A.Persaud and J.A. Liddle and J.Nilsson and J.Bokor and D.H. Schneider and I.W. Rangelow and T.Schenkel",
title = "Processing issues in top-down approaches to quantum computer development in silicon",
journal = "Microelectronic Engineering",
volume = "73--74",
eprint = "cond-mat/0310195",
year = "2004",
pages = "695--700",
}
A.Persaud, S.J. Park, J.A. Liddle, I.W. Rangelow, J.Bokor, R.Keller, F.I. Allen, D.H. Schneider and T.Schenkel Quantum Computer Development with Single Ion Implantation Quantum Information Processing 3 233--245 (2004) pdf bibtex
@article{ Persaud:QIP-3-233,
author = "A.Persaud and S.J. Park and J.A. Liddle and I.W. Rangelow and J.Bokor and R.Keller and F.I. Allen and D.H. Schneider and T.Schenkel",
title = "Quantum Computer Development with Single Ion Implantation",
journal = "Quantum Information Processing",
volume = "3",
year = "2004",
pages = "233--245",
}

2003

T.Schenkel, A.Persaud, S.J. Park, J.Nilsson, J.Bokor, J.A. Liddle, R.Keller, D.H. Schneider, D.W. Cheng and D.E. Humphries Solid state quantum computer development in silicon with single ion implantation Journal of Applied Physics 94(11) 7017--7024 (2003) bibtex
@article{ Schenkel:JAP-94-7017,
author = "T.Schenkel and A.Persaud and S.J. Park and J.Nilsson and J.Bokor and J.A. Liddle and R.Keller and D.H. Schneider and D.W. Cheng and D.E. Humphries",
title = "Solid state quantum computer development in silicon with single ion implantation",
journal = "Journal of Applied Physics",
number = "11",
volume = "94",
year = "2003",
pages = "7017--7024"
}

2002

T.Schenkel, J.P. Holder, J.W. McDonald, J.Meijer, A.Persaud and D.H. Schneider Single Ion Implantation for Solid State Quantum Computer Development in SPIE V4656 (2002) pdf arXiv.org bibtex
@inproceedings{ Schenkel2002_SPIE,
author = "T.Schenkel and J.P. Holder and J.W. McDonald and J.Meijer and A.Persaud and D.H. Schneider",
title = "Single Ion Implantation for Solid State Quantum Computer Development",
booktitle = "SPIE V4656",
eprint = "cond-mat/0201549",
year = "2002",
organization = "SPIE",
address = "San Jose",
}
T.Schenkel, A.Persaud, S.J. Park, J.Meijer, J.R. Kinglsey, J.W. McDonald, J.P. Holder, J.Bokor and D.H. Schneider Single Ion Implantation for Solid State Quantum Computer Development Journal of Vacuum Science and Technology B 20(6) 2819--2823 (2002) pdf arXiv.org bibtex
@article{ Schenkel:JVSTB-20-2816,
author = "T.Schenkel and A.Persaud and S.J. Park and J.Meijer and J.R. Kinglsey and J.W. McDonald and J.P. Holder and J.Bokor and D.H. Schneider",
title = "Single Ion Implantation for Solid State Quantum Computer Development",
journal = "Journal of Vacuum Science and Technology B",
number = "6",
volume = "20",
eprint = "cond-mat/0201549",
year = "2002",
pages = "2819--2823",
}