Quantum mechanics offers the opportunity for completely new ways of encoding and processing information in future quantum devices of unprecedented power. Development of quantum computers is a highly ambitious technological pursuit that can provide dramatic payoff with speedups in tasks of interest to the DOD, including the ability to break codes that are fundamentally unbreakable with ordinary computers. Quantum information also offers impressive improvements in secure communication and sensing. Our team is working to establish the scientific basis for practical solid state quantum information technologies using the spin states of semiconductor quantum dots (QDs) and defects in solids. These systems have the advantage of a robust solid state host, the ability to produce many qubits on chip, coupling to photons, and the ability to incorporate qubits into sophisticated electronic, photonic, and mechanical devices. Over the past two decades we have made key advances in materials and devices, optical techniques for control and measurement, and in the underlying physics.

Our team consists of a multidisciplinary group of experts in materials growth, fabrication, spectroscopy and theory: Dan Gammon, Allan Bracker, Sam Carter, and Tom Reinecke. We have in-house access to all of the laboratory and computing resources required for this effort, including the molecular beam epitaxy growth facility; SiC epitaxy; characterization tools (STM, AFM, x-ray diffraction); the Nanoscience Institute cleanroom; and several optical spectroscopy labs with multiple cryostats, pulsed and cw laser systems, spectrometers, and detectors. Since 2005, this team has published over 35 papers in the journals Science, Nature, and Physical Review Letters with over 1600 total citations.

Key contributions and ongoing efforts of this team include:

1. Quantum Dot Growth and Device Fabrication
  • Engineering of orbital and spin energy levels of QDs
  • Engineering of multi-qubit structures with stacked QDs
  • Deterministic control of QD position with nanometer precision
  • Incorporation of dots into electrical and photonic devices
2. Quantum Control and Entanglement
  • Design and implementation of quantum logic gates of spins using laser pulses
  • Identification, modeling, and mitigation of loss and decoherence due to interaction with QD nuclear spins
  • First demonstration of ultrafast entanglement control of two spin qubits in QDs
3. Quantum Nanophotonics
  • Integration of QD qubits into photonic crystal circuits
  • Conversion of quantum information between solid state and photonic qubits
  • Design of entangled multiphoton “cluster” states from QDs
  • First demonstration of quantum gates on a spin qubit coupled to a nanocavity.
  • Single and entangled photon emission from photonic structures
4. Hybrid Quantum Dot/Mechanical Systems
  • Integration of QD qubits in mechanical resonators for sensing motion/acceleration
  • Maximizing coupling between entangled spins in QDs and motion through strain
  • Cooling mechanical motion through QDs
5. Defect Spins in SiC and Diamond
  • Measuring and maximizing spin coherence using microwave and optical pulses
  • Fabrication of photonic and mechanical structures with integrated defects
  • Materials development in epitaxial films of SiC

Selected Publications

2019 Banks, H. B., Ö. O. Soykal, R. Myers-Ward, D. K. Gaskill, T. L. Reinecke, and S. G. Carter, "Resonant optical spin initialization and readout of single silicon vacancies in 4H-SiC", Physical Review Applied, vol. vol 11, issue 024013 , 2019.
2019 Grim, J. Q., A. S. Bracker, M. Zalalutdinov, S. G. Carter, A. C. Kozen, M. Kim, C. S. Kim, J. T. Mlack, M. Yakes, B. Lee, et al., "Scalable in operando strain tuning in nanophotonic waveguides enabling three- quantum-dot superradiance", Nature Materials, vol. 18, 2019. PDF icon Grim_Strain_tuning_QDs_published.pdf (1.96 MB)
2019 Lee, B., B. C. Pursley, S. G. Carter, S. E. Economou, M. K. Yakes, J. Q. Grim, A. S. Bracker, and D. Gammon, "Spin-dependent quantum optics in a quantum dot molecule", Physical Review B, vol. vol 100, issue 125438, 2019. PDF icon QDM quantum light published.pdf (1.42 MB)
2019 Carter, S. G., A. S. Bracker, M. K. Yakes, M. K. Zalalutdinov, M. Kim, C. S. Kim, B. Lee, and D. Gammon, "Tunable coupling of a double quantum dot spin system to a mechanical resonator", Nano Letters, vol. vol 19, issue 6166, 2019. PDF icon Carter_Spin-Mech_PRL2018.pdf (798 KB)
2018 Carter, S. G., A. S. Bracker, M. K. Yakes, M. K. Zalalutdinov, M. Kim, M. K. Zalalutdinov, M. K. Yakes, C. Czarnocki, J. Casara, M. Scheibner, et al., "Spin-mechanical coupling of an InAs quantum dot embedded in a mechanical resonator", Physical Review Letters, vol. 121, 2018. PDF icon QDM spin mech published.pdf (1.22 MB)
2018 Pursley, B. C., S. G. Carter, M. K. Yakes, A. S. Bracker, and D. Gammon, "Picosecond pulse shaping of single photons using quantum dots", Nature Communications, vol. vol 9, issue 115, 2018. PDF icon Pursley_et_al-2018-Nature_Communications.pdf (921.22 KB)
2017 Carter, S. G., A. S. Bracker, M. K. Yakes, M. K. Zalalutdinov, M. Kim, C. S. Kim, C. Czarnocki, M. Scheibner, and D. Gammon, "Sensing flexural motion of a photonic crystal membrane with InGaAs quantum dots", Applied Physics Letters, , pp. 23310, 2017. PDF icon Carter_Spin-Mech_PRL2018.pdf (798 KB)
2016 Yang, L., S. G. Carter, A. S. Bracker, M. K. Yakes, M. Kim, C. S. Kim, P. M. Vora, and D. Gammon, "Optical spectroscopy of site-controlled quantum dots in a Schottky diode", Appl. Phys. Lett. , vol. 108, issue 233102, 2016. PDF icon Yang_spectroscopy_site-controlled_QDs_APL2016.pdf (1.52 MB)
2015 Vora, P. M., A. S. Bracker, S. G. Carter, T. M. Sweeney, M. Kim, C. S. Kim, L. Yang, P. G. Brereton, S. Economou, and D. Gammon, "Spin–cavity interactions between a quantum dot molecule and a photonic crystal cavity", Nature Communications, 2015.
2015 Carter, S. G., Ö. O. Soykal, P. Dev, S. E. Economou, and E. R. Glaser, "Spin coherence and echo modulation of the silicon vacancy in 4H-SiC at room temperature", Physical Review B, vol. 92, issue 161202, 2015. PDF icon Spin_echo-PRB_published.pdf (593.86 KB)
2014 Sweeney, T. M., S. G. Carter, A. S. Bracker, M. Kim, C. S. Kim, L. Yang, P. M. Vora, P. G. Brereton, E. R. Cleveland, and D. Gammon, "Cavity-Stimulated Raman Emission from a Single Quantum Dot Spin", Nature Photonics, vol. 8, 2014.
2014 Carter, S. G., S. E. Economou, A. Greilich, E. Barnes, T. M. Sweeney, A. S. Bracker, and D. Gammon, "Strong Hyperfine-Induced Modulation of an Optically-Driven Hole Spin in an InAs Quantum Dot", Phys. Rev. B, vol. 89, 2014.
2013 Carter, S. G., T. M. Sweeney, M. Kim, C. S. Kim, D. Solenov, S. Economou, T. Reinecke, L. Yang, A. Bracker, and D. Gammon, "Quantum control of a spin qubit coupled to a photonic crystal cavity", Nature Photonics, vol. 7, issue 4, 2013. PDF icon Carter PhC qubit.pdf (992.15 KB)
2013 Yakes, M. K., L. Yang, A. Bracker, T. M. Sweeney, P. G. Brereton, M. Kim, C. S. Kim, P. M. Vora, D. Park, S. G. Carter, et al., "Leveraging crystal anisotropy for deterministic growth of InAs quantum dots with narrow optical linewidths", Nano Letters, vol. 13, issue 10, pp. 4870-4875, 2013. PDF icon nl402744s.pdf (3.82 MB)
2013 Greilich, A., S. C. Badescu, D. Kim, A. Bracker, and D. Gammon, "Optical Measurement and Modeling of Interactions between Two Hole Spins or Two Electron Spins in Coupled InAs Quantum Dots", Physical Review Letters, vol. 110, issue 11, 2013. PDF icon e117402.pdf (853.13 KB)
2011 Greilich, A., S. G. Carter, D. Kim, A. Bracker, and D. Gammon, "Optical control of one and two hole spins in interacting quantum dots", Nature Photonics, vol. 5, issue 11, pp. 703-709, 2011. PDF icon 11-1226-3607.pdf (247.3 KB)
2011 Carter, S. G., S. Economou, A. Shabaev, and A. Bracker, "Controlling the nuclear polarization in quantum dots using optical pulse shape", Physical Review B, vol. 83, 2011. PDF icon 10-1226-4261.pdf (571.62 KB)
2010 Yakes, M. K., C. D. Cress, J. G. Tischler, and A. Bracker, "Three-Dimensional Control of Self-Assembled Quantum Dot Configurations", ACS Nano, vol. 4, issue 7, pp. 3877-3882, 2010. PDF icon 10-1226-2510.pdf (317.94 KB)
2010 Kim, D., S. G. Carter, A. Greilich, A. Bracker, and D. Gammon, "Ultrafast optical control of entanglement between two quantum dot spins", Nature Physics, vol. 7, pp. 223-229, 2010. PDF icon 10-1226-4276.pdf (436.28 KB)
2010 Carter, S. G., S. C. Badescu, and A. Bracker, "Electronic spin polarization and detection in InAs quantum dots through p-shell trions", Physical Review B, vol. 81, 2010. PDF icon 09-1226-3623.pdf (273.53 KB)
2009 Doty, M. F., J. I. Climente, M. Korkusinski, M. Scheibner, A. Bracker, P. Hawrylak, and D. Gammon, "Antibonding ground states in InAs quantum dot molecules", Physical Review Letters, vol. 102, 2009. PDF icon 08-1226-4126.pdf (2.04 MB)
2009 Carter, S. G., A. Shabaev, S. Economou, T. A. Kennedy, A. Bracker, and T. Reinecke, "Directing Nuclear Spin Flips in InAs Quantum Dots Using Detuned Optical Pulse Trains", Physical Review Letters, vol. 102, 2009. PDF icon 09-1226-0054.pdf (414.14 KB)
2008 Kim, D., S. Economou, S. C. Badescu, M. Scheibner, A. Bracker, M. Bashkansky, T. Reinecke, and D. Gammon, "Optical spin spin initialization and nondestructive measurement in a quantum dot molecule", Physical Review Letters, vol. 101, 2008. PDF icon 08-1226-3576.pdf (1.08 MB)
2008 Scheibner, M., M. K. Yakes, A. Bracker, I. V. Ponomarev, M. F. Doty, C. S. Hellberg, L. J. Whitman, T. Reinecke, and D. Gammon, "Optically mapping the electronic structure of coupled quantum dots", Nature Physics, vol. 4, 2008. PDF icon 08-1226-0001.pdf (1.18 MB)
2007 Scheibner, M., I. V. Ponomarev, E. A. Stinaff, M. F. Doty, A. Bracker, C. S. Hellberg, T. Reinecke, and D. Gammon, "Photoluminescence spectroscopy of the molecular biexciton in vertically stacked InAs-GaAs quantum dot pairs", Physical Review Letters, vol. 99, 2007. PDF icon 07-1226-3326.pdf (1.15 MB)
2006 Doty, M. F., M. Scheibner, I. V. Ponomarev, E. A. Stinaff, A. Bracker, V. L. Korenev, T. Reinecke, and D. Gammon, "Electrically Tunable g Factors in Quantum Dot Molecular Spin States", Physical Review Letters, vol. 97, 2006. PDF icon 06-1226-3198.pdf (760 KB)
2006 Bracker, A., M. Scheibner, M. F. Doty, E. A. Stinaff, I. V. Ponomarev, J. Kim, L. J. Whitman, T. Reinecke, and D. Gammon, "Engineering Electron and Hole Tunneling with Asymmetric InAs Quantum Dot Molecules", Applied Physics Letters, vol. 89, 2006. PDF icon 06-1226-3026.pdf (324.85 KB)
2005 Bracker, A., E. A. Stinaff, D. Gammon, M. E. Ware, J. G. Tischler, A. Shabaev, A. L. Efros, D. Park, D. Gershoni, V. L. Korenev, et al., "Optical Pumping of the Electronic and Nuclear spin of Single Charge-Tunable Quantum Dots", Physical Review Letters, vol. 94, 2005. PDF icon 04-1226-1081.pdf (177.85 KB)
2002 Gammon, D., and D. G. Steel, "Optical Studies of Single Quantum Dots", Physics Today, vol. 55, issue 10, 2002. PDF icon 02-1221.1-3008.pdf (1.16 MB)