scholarly journals Holonomic implementation of CNOT gate on topological Majorana qubits

2020 ◽  
Vol 3 (2) ◽  
Author(s):  
Alessio Calzona ◽  
Nicolas Bauer ◽  
Björn Trauzettel
Keyword(s):  
Quantum Computation ◽  
Cnot Gate ◽  
Alternative Scheme ◽  
System Parameters ◽  
Universal Quantum ◽  
Subsequent Measurement ◽  
Qubit Gate

The CNOT gate is a two-qubit gate which is essential for universal quantum computation. A well-established approach to implement it within Majorana-based qubits relies on subsequent measurement of (joint) Majorana parities. We propose an alternative scheme which operates a protected CNOT gate via the holonomic control of a handful of system parameters, without requiring any measurement. We show how the adiabatic tuning of pair-wise couplings between Majoranas can robustly lead to the full entanglement of two qubits, insensitive with respect to small variations in the control of the parameters.

scholarly journals Two-qubit sweet spots for capacitively coupled exchange-only spin qubits

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
MengKe Feng ◽  
Lin Htoo Zaw ◽  
Teck Seng Koh
Keyword(s):  
Quantum Dot ◽  
Quantum Computation ◽  
Parameter Space ◽  
Capacitive Coupling ◽  
High Fidelity ◽  
Spin Qubits ◽  
Capacitively Coupled ◽  
Universal Quantum ◽  
Qubit Gate ◽  
Sweet Spots

AbstractThe implementation of high fidelity two-qubit gates is a bottleneck in the progress toward universal quantum computation in semiconductor quantum dot qubits. We study capacitive coupling between two triple quantum dot spin qubits encoded in the S = 1/2, Sz = −1/2 decoherence-free subspace—the exchange-only (EO) spin qubits. We report exact gate sequences for CPHASE and CNOT gates, and demonstrate theoretically, the existence of multiple two-qubit sweet spots (2QSS) in the parameter space of capacitively coupled EO qubits. Gate operations have the advantage of being all-electrical, but charge noise that couple to electrical parameters of the qubits cause decoherence. Assuming noise with a 1/f spectrum, two-qubit gate fidelities and times are calculated, which provide useful information on the noise threshold necessary for fault-tolerance. We study two-qubit gates at single and multiple parameter 2QSS. In particular, for two existing EO implementations—the resonant exchange (RX) and the always-on exchange-only (AEON) qubits—we compare two-qubit gate fidelities and times at positions in parameter space where the 2QSS are simultaneously single-qubit sweet spots (1QSS) for the RX and AEON. These results provide a potential route to the realization of high fidelity quantum computation.

scholarly journals Universal quantum computation with shutter logic

2006 ◽  
Vol 6 (6) ◽  
pp. 495-515
Author(s):  
J.C. Garcia-Escartin ◽  
P. Chamorro-Posada
Keyword(s):  
Quantum Computation ◽  
Quantum Logic ◽  
Quantum Computer ◽  
Quantum Memory ◽  
Linear Optics ◽  
Cnot Gate ◽  
Free Model ◽  
Universal Quantum

We show that universal quantum logic can be achieved using only linear optics and a quantum shutter device. With these elements, we design a quantum memory for any number of qubits and a CNOT gate which are the basis of a universal quantum computer. An interaction-free model for a quantum shutter is given.

Both Toffoli and Controlled-NOT need little help to universal quantum computing

2003 ◽  
Vol 3 (1) ◽  
pp. 84-92
Author(s):  
Y-Y Shi
Keyword(s):  
Quantum Computing ◽  
Quantum Computation ◽  
Quantum Circuit ◽  
Single Qubit ◽  
Universal Quantum ◽  
Qubit Gate ◽  
Computational Basis ◽  
Universal Gates

What additional gates are needed for a set of classical universal gates to do universal quantum computation? We prove that any single-qubit real gate suffices, except those that preserve the computational basis. The Gottesman-Knill Theorem implies that any quantum circuit involving only the Controlled-NOT and Hadamard gates can be efficiently simulated by a classical circuit. In contrast, we prove that Controlled-NOT plus any single-qubit real gate that does not preserve the computational basis and is not Hadamard (or its like) are universal for quantum computing. Previously only a generic gate, namely a rotation by an angle incommensurate with \pi, is known to be sufficient in both problems, if only one single-qubit gate is added.

scholarly journals Extending matchgates into universal quantum computation

2011 ◽  
Vol 84 (2) ◽  
Author(s):  
Daniel J. Brod ◽  
Ernesto F. Galvão
Keyword(s):  
Quantum Computation ◽  
Universal Quantum

Universal quantum computation with quantum-dot cellular automata in decoherence-free subspace

2008 ◽  
Vol 8 (10) ◽  
pp. 977-985
Author(s):  
Z.-Y. Xu ◽  
M. Feng ◽  
W.-M. Zhang
Keyword(s):  
Cellular Automata ◽  
Quantum Dot ◽  
Quantum Computation ◽  
Two Dimensions ◽  
High Fidelity ◽  
Electron Pairs ◽  
Quantum Dot Cellular Automata ◽  
Single Spin ◽  
Universal Quantum ◽  
Decoherence Free Subspace

We investigate the possibility to have electron-pairs in decoherence-free subspace (DFS), by means of the quantum-dot cellular automata (QCA) and single-spin rotations, to deterministically carry out a universal quantum computation with high-fidelity. We show that our QCA device with electrons tunneling in two dimensions is very suitable for DFS encoding, and argue that our design favors a scalable quantum computation robust to collective dephasing errors.

scholarly journals Roads towards fault-tolerant universal quantum computation

Nature ◽  
2017 ◽  
Vol 549 (7671) ◽  
pp. 172-179 ◽  
Author(s):  
Earl T. Campbell ◽  
Barbara M. Terhal ◽  
Christophe Vuillot
Keyword(s):  
Quantum Computation ◽  
Fault Tolerant ◽  
Universal Quantum
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