Simulation of Si:P spin-based quantum computer architecture

Fang, Angbo; Chang, Yia‐Chung; Tucker, J. R.

doi:10.1103/physrevb.72.075355

Cited by 18 publications

(21 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The competition between the two is one of the central issues of condensed matter physics [1][2][3][4][5][6]. A microscopic study of this competition is often difficult for two reasons: one, most systems involve some form of intervening phases such as magnetic order observed in the parent state of cuprate [3] or cobaltate [4] superconductors; two, there lacks systematically tunable electronic parameters compatible with microscopic k-space imaging techniques such as angle-resolved photoemission spectroscopy (ARPES).…”

mentioning

confidence: 99%

Emergence of Fermi Pockets in a New Excitonic Charge-Density-Wave Melted Superconductor

et al. 2007

View full text Add to dashboard Cite

A superconducting state (T c 4:2 K) has very recently been observed upon successful doping of the charge-density-wave (CDW) ordered triangular lattice TiSe 2 , with copper. Using state-of-the-art photoemission spectroscopy we identify, for the first time, momentum-space locations of doped electrons that form the Fermi sea of the superconductor. With doping, we find that kinematic nesting volume increases, whereas coherence of the CDW collective order sharply drops. In superconducting doping, as chemical potential rises, we observe the emergence of a large density of states in the form of a narrow electron pocket near the L point of the Brillouin zone with d-like character. The k-space spectral evolution directly demonstrates, for the first time, that the CDW order parameter microscopically competes with superconductivity in the same band.

show abstract

mentioning

confidence: 99%

Emergence of Fermi Pockets in a New Excitonic Charge-Density-Wave Melted Superconductor

et al. 2007

View full text Add to dashboard Cite

show abstract

“…[4] Recently, Morosan et al discovered an interesting new material exhibiting a competition between CDW order and SC: copper intercalated 1T -TiSe 2 , i.e., Cu x TiSe 2 . [5] 1T -TiSe 2 is a semimetal or small-gap semiconductor in the normal state, [6,7,8,9] which develops a commensurate CDW with a 2a o ×2a o ×2c o superlattice structure at temperatures below a second-order phase transition at T CDW ∼ 200 K. [6,10] Increasing Cu intercalation in TiSe 2 (increasing x in Cu x TiSe 2 ) results in (i) an expansion of the a-and c-axis lattice parameters, [5] (ii) increased electronic density of states near the L point, [7,8] (iii) a suppression of the CDW transition temperature, [5] and (iv) the emergence near x = 0.04 of a SC phase having a maximum T c of 4.15 K at x = 0.08.…”

mentioning

confidence: 99%

Quantum and Classical Mode Softening Near the Charge-Density-Wave–Superconductor Transition ofCuxTiSe2

et al. 2008

View full text Add to dashboard Cite

Temperature-and x-dependent Raman scattering studies of the charge density wave (CDW) amplitude modes in CuxTiSe2 show that the amplitude mode frequency ωo exhibits identical powerlaw scaling with the reduced temperature, T/TCDW, and the reduced Cu content, x/xc, i.e., ωo ∼ (1 -p) 0.15 for p = T/TCDW or x/xc, suggesting that mode softening is independent of the control parameter used to approach the CDW transition. We provide evidence that x-dependent mode softening in CuxTiSe2 is caused by the reduction of the electron-phonon coupling constant λ due to expansion of the lattice, and that x-dependent 'quantum' (T ∼ 0) mode softening reveals a quantum critical point within the superconductor phase of CuxTiSe2. 1T -TiSe 2 is a semimetal or small-gap semiconductor in the normal state, [6,7,8,9] which develops a commensurate CDW with a 2a o ×2a o ×2c o superlattice structure at temperatures below a second-order phase transition at T CDW ∼ 200 K. [6,10] Increasing Cu intercalation in TiSe 2 (increasing x in Cu x TiSe 2 ) results in (i) an expansion of the a-and c-axis lattice parameters, [5] (ii) increased electronic density of states near the L point, [7,8] (iii) a suppression of the CDW transition temperature, [5] and (iv) the emergence near x = 0.04 of a SC phase having a maximum T c of 4.15 K at x = 0.08. [5] The Cu x TiSe 2 system provides an ideal opportunity to investigate the microscopic details of quantum (T ∼ 0) phase transitions between CDW order and SC. It is of particular interest to clarify the nature of the "soft mode" in CDW/SC transitions: the behavior of the soft mode -i.e., the phonon mode whose eigenvector mimics the CDW lattice distortion, and hence whose frequency tends towards zero at the second-order phase transition -is one of the most fundamental and well-studied phenomena associated with classical (thermally driven) displacive phase transitions;[11] on the other hand, soft mode behavior associated with quantum phase transitions is not well understood. In this investigation, we use Raman scattering to study the temperature-and dopingdependent evolution of the CDW 'amplitude' modes in Cu x TiSe 2 . The CDW amplitude mode [12] -which is associated with collective transverse fluctuations of the CDW order parameter -offers detailed information regarding the evolution and stability of the CDW state and the CDW soft mode. In this study, we show that the amplitude mode frequency in Cu x TiSe 2 exhibits identical power-law scaling with the reduced temperature, T/T CDW , and the reduced Cu content, x/x c , indicating that mode softening in Cu x TiSe 2 is independent of the control parameter used to approach the CDW transition. Further, we show that 'quantum' (T ∼ 0) softening of the CDW amplitude mode is consistent with a quantum critical point hidden in the superconductor phase of Cu x TiSe 2 , suggesting a possible connection between quantum criticality and superconductivity.Raman scattering measurements were performed on high quality single-crystal and pressed-pellet samples of Cu x TiSe 2 for x = ...

show abstract

“…By carrying out this procedure over a wide range of gate voltages, a much clearer indication of the possible performance of this architecture has emerged. [14] Figure 11. Gate-induced potential (in units of Ry*~30meV) for two sets of applied voltages.…”

Section: Fabrication and Testing Of Buried P Donor Nanowiresmentioning

confidence: 99%

“…Extensive simulations have been carried out on this silicon-based quantum computer architecture to assess prospects for a successful implementation. [14] An in-plane expansion of the strained Si crystal lattice lifts the 6-valley degeneracy, leaving the two perpendicular z valleys lower in energy by ~100meV from which the low-lying bound states must be constructed. Figure 10 shows the calculated energies of the two lowest bound states of an individual P donor electron as a function of quantum well thickness, together with their splitting.…”

Section: Fabrication and Testing Of Buried P Donor Nanowiresmentioning

confidence: 99%

Wavefunction Engineering of Individual Donors for Silicon-Based Quantum Computers

Tucker¹

2005

View full text Add to dashboard Cite

Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. This project has explored possibilities for realizing a Kane-type quantum computer based on Si:P donor qubits. The overall goal has been to create an integrated process based on STM patterning of individual P-donor qubits, combined with single-electron transistors (SETs) for singlet-triplet spin state detection in the same lithographic step. The main accomplishments during this period have been to: (1) develop processes for positioning P atom donors and self-ordered arrays with near-atomic accuracy inside the silicon crystal lattice, (2) fabricate P donor nanowires as a major step toward an integrated epitaxial single-electron transistor, (3) measure electrical characteristics of the unpatterned P δ-layer and P donor nanowires, (4) compare the electrical data with our band structure calculations on the P δ-layer and previous theories of weak localization, (5) propose a new Kane-type architecture employing the idea of 'universal exchange' based on composite 3-electron spin qubits, and (6) perform extensive simulations to confirm the fundamental aspects of this approach, and quantify major difficulties to be overcome. Sustained effort in these directions will be required to realize a working qubit.

show abstract

Simulation of Si:P spin-based quantum computer architecture

Cited by 18 publications

References 42 publications

Emergence of Fermi Pockets in a New Excitonic Charge-Density-Wave Melted Superconductor

Emergence of Fermi Pockets in a New Excitonic Charge-Density-Wave Melted Superconductor

Quantum and Classical Mode Softening Near the Charge-Density-Wave–Superconductor Transition ofCuxTiSe2

Wavefunction Engineering of Individual Donors for Silicon-Based Quantum Computers

Contact Info

Product

Resources

About