54 citations · 221 across the 15 of their papers we have counts for
15 papers
Demonstration of system-bath physics on a gate-based quantum computer
Pascal Stadler, Matteo Lodi, Andisheh Khedri +5
Algorithmic cooling can be used to find correlated states of many-body quantum systems. It is based on quantum circuits that perform nonunitary operations, whose implementation can…
A quantum algorithm for solving open system dynamics on quantum computers using noise
Juha Leppäkangas, Nicolas Vogt, Keith R. Fratus +6
In this paper we present a quantum algorithm that uses noise as a resource. The goal of our quantum algorithm is the calculation of operator averages of an open quantum system evol…
Describing Trotterized Time Evolutions on Noisy Quantum Computers via Static Effective Lindbladians
Keith R. Fratus, Kirsten Bark, Nicolas Vogt +4
We consider the extent to which a Trotterized time evolution implemented on a quantum computer is altered by the presence of decoherence. Given a specific set of assumptions regard…
Analyzing the spectral density of a perturbed analog quantum simulator using Keldysh formalism
Sebastian Zanker, Iris Schwenk, Jan-Michael Reiner +2
Simulation of interacting electron systems is one of the great challenges of modern quantum chemistry and solid state physics. Controllable quantum systems offer the opportunity to…
Reconstructing the ideal results of a perturbed analog quantum simulator
Iris Schwenk, Jan-Michael Reiner, Sebastian Zanker +3
Well-controlled quantum systems can potentially be used as quantum simulators. However, a quantum simulator is inevitably perturbed by coupling to additional degrees of freedom. Th…
Multiplying and detecting propagating microwave photons using inelastic Cooper-pair tunneling
Juha Leppäkangas, Michael Marthaler, Dibyendu Hazra +5
The interaction between propagating microwave fields and Cooper-pair tunneling across a DC voltage-biased Josephson junction can be highly nonlinear. We show theoretically that thi…
Estimating the error of an analog quantum simulator by additional measurements
Iris Schwenk, Sebastian Zanker, Jan-Michael Reiner +2
We study an analog quantum simulator coupled to a reservoir with a known spectral density. The reservoir perturbs the quantum simulation by causing decoherence. The simulator is us…
Creating photon-number squeezed strong microwave fields by a Cooper-pair injection laser
Martin Koppenhöfer, Juha Leppäkangas, Michael Marthaler
The use of artificial atoms as an active lasing medium opens a way to construct novel sources of nonclassical radiation. An example is the creation of photon-number squeezed light.…
Correlated Cooper pair transport and microwave photon emission in the dynamical Coulomb blockade
Juha Leppäkangas, Mikael Fogelström, Michael Marthaler +1
We study theoretically electromagnetic radiation emitted by inelastic Cooper-pair tunneling. We consider a dc-voltage-biased superconducting transmission line terminated by a Josep…
Diagrammatic description of a system coupled strongly to a bosonic bath
Michael Marthaler, Juha Leppäkangas
We study a system-bath description in the strong coupling regime where it is not possible to derive a master equation for the reduced density matrix by a direct expansion in the sy…
Fully superconducting Bloch-oscillating transistor: Amplification and bifurcation based on Bloch oscillations and counterflowing Cooper pairs
J. Leppäkangas, A. Puska, L. Äkäslompolo +2
The Bloch-oscillating transistor (BOT) is an amplifier that utilizes semiclassical dynamics of states in energy bands under traveling quasimomentum. In a BOT, a single quasiparticl…
Nonclassical photon pair production in a voltage-biased Josephson junction
Juha Leppäkangas, Göran Johansson, Michael Marthaler +1
We investigate electromagnetic radiation emitted by a small voltage-biased Josephson junction connected to a superconducting transmission line. At frequencies below the well known…
Sub-Poissonian photon statistics in a strongly coupled single-qubit laser
M. Marthaler, Pei-Qing Jin, Juha Leppäkangas +1
We investigate qubit lasing in the strong coupling limit. The qubit is given by a Cooper-pair box, and population inversion is established by an additional third state, which can b…
Fragility of multi-junction flux qubits against quasiparticle tunneling
Juha Leppäkangas, Michael Marthaler
We study decoherence in superconducting qubits due to quasiparticle tunneling which is enhanced by two known deviations from the equilibrium BCS theory. The first process correspon…
Phase-dependent quasiparticle tunneling in Josephson junctions: Measuring the cos-phi term with a superconducting charge qubit
Juha Leppäkangas, Michael Marthaler, Gerd Schön
We investigate quasiparticle tunneling in a Cooper-pair box which is embedded in a superconducting ring to allow control of the total phase difference across the island. The phase…