Can We Build a Large-Scale Quantum Computer Using Semiconductor Materials?

Abstract

The following article is based on the Symposium X presentation given by Bruce E. Kane (University of Maryland) at the 2004 Materials Research Society Spring Meeting in San Francisco. Quantum computing has the potential to revolutionize our ability to solve certain classes of difficult problems. A quantum computer is able to manipulate individual two-level quantum states (“qubits”) in the same way that a conventional computer processes binary ones and zeroes. Here, Kane discusses some of the most promising proposals for quantum computing, in which the qubit is associated with single-electron spins in semiconductors. While current research is focused on devices at the one- and two-qubit level, there is hope that cross-fertilization with advancing conventional computer technology will enable the eventual development of a large-scale (thousands of qubits) semiconductor quantum computer.The author focuses on materials issues that will need to be surmounted if large-scale quantum computing is to be realizable. He argues in particular that inherent fluctuations in doped semiconductors will severely limit scaling and that scalable quantum computing in semiconductors may only be possible at the end of the road of Moore's law scaling, when devices are engineered and fabricated at the atomic level.

Magnetic-field-assisted manipulation and entanglement of Si spin qubits

“…2(c), F = F c +120 V/cm and the needed field is B ∼ 3.2 T. Therefore, fine tuning of the electric field is required to observe this phenomenon at reasonably small magnetic fields. We propose to use this result as a means of differentiating donor electrons from other charges that may be detected [10] in the architecture shown in Fig. 1(a).…”

Quantum Control of Donor Electrons at theSi−SiO2Interface

“…Silicon-based structures are among the most promising candidates for the development of a quantum computer [1][2][3][4][5][6][7] due to the existing high level of nanofabrication control as well as the well-established scalability advantages of Si microelectronics. Different architectures have been proposed in which nuclear spin [1,3], electron spin [2], or electron charge [4] are used as qubits.…”

Quantum computation with doped silicon cavities

“…Experimental advances in solid-state proposals are still focused at the one-and two-qubit levels. 10,11 The perspective of benefiting from the available microelectronics technology brings continuous attention from the QC community to semiconductor quantum devices, [12][13][14] particularly those based on silicon. [15][16][17][18][19][20][21][22][23][24][25] Successful experimental efforts in single donor control demonstrate the potential of isolated donors in Si for applications in electronic nanodevices.…”

“…Semiconductor devices [5,6], and most particularly those based on silicon [7], have attracted considerable attention, but actual realization is hindered by difficulties concerning scalability, detection and fabrication [8]. Most candidates for a semiconductor-based quantum computer rely on spin-1/2 fermion qubits [9], which for Si may be associated to the long-lived electron and nuclear spins of shallow substitutional donors [7].…”

“…Implementation of quantum computation with these systems is hindered by several problems. The most obvious [8] is the difficulty in the manipulation and measurement of single-spin states. Two-qubit operations relying on exchange gates [5], restricted to nearestneighbor interactions, have limited scalability potential [11].…”