20 research outputs found
Efficient qubit routing for a globally connected trapped ion quantum computer
The cost of enabling connectivity in noisy intermediate‐scale quantum (NISQ) devices is an important factor in determining computational power. A qubit routing algorithm is created, which enables efficient global connectivity in a previously proposed trapped ion quantum computing architecture. The routing algorithm is characterized by comparison against both a strict lower bound, and a positional swap based routing algorithm. An error model is proposed, which can be used to estimate the achievable circuit depth and quantum volume of the device as a function of experimental parameters. A new metric based on quantum volume, but with native two‐qubit gates, is used to assess the cost of connectivity relative to the upper bound of free, all to all connectivity. The metric is also used to assess a square‐grid superconducting device. These two architectures are compared and it is found that for the shuttling parameters used, the trapped ion design has a substantially lower cost associated with connectivity
Optimisation of two-dimensional ion trap arrays for quantum simulation
The optimisation of two-dimensional (2D) lattice ion trap geometries for
trapped ion quantum simulation is investigated. The geometry is optimised for
the highest ratio of ion-ion interaction rate to decoherence rate. To calculate
the electric field of such array geometries a numerical simulation based on a
"Biot-Savart like law" method is used. In this article we will focus on square,
hexagonal and centre rectangular lattices for optimisation. A method for
maximising the homogeneity of trapping site properties over an array is
presented for arrays of a range of sizes. We show how both the polygon radii
and separations scale to optimise the ratio between the interaction and
decoherence rate. The optimal polygon radius and separation for a 2D lattice is
found to be a function of the ratio between rf voltage and drive frequency
applied to the array. We then provide a case study for 171Yb+ ions to show how
a two-dimensional quantum simulator array could be designed
Doppler-free Yb Spectroscopy with Fluorescence Spot Technique
We demonstrate a simple technique to measure the resonant frequency of the
398.9 nm 1S0 - 1P1 transition for the different Yb isotopes. The technique,
that works by observing and aligning fluorescence spots, has enabled us to
measure transition frequencies and isotope shifts with an accuracy of 60 MHz.
We provide wavelength measurements for the transition that differ from
previously published work. Our technique also allows for the determination of
Doppler shifted transition frequencies for photoionisation experiments when the
atomic beam and laser beam are not perpendicular and furthermore allows us to
determine the average velocity of the atoms along the direction of atomic beam
The impact of hardware specifications on reaching quantum advantage in the fault tolerant regime
We investigate how hardware specifications can impact the final run time and
the required number of physical qubits to achieve a quantum advantage in the
fault tolerant regime. Within a particular time frame, both the code cycle time
and the number of achievable physical qubits may vary by orders of magnitude
between different quantum hardware designs. We start with logical resource
requirements corresponding to a quantum advantage for a particular chemistry
application, simulating the FeMoco molecule, and explore to what extent slower
code cycle times can be mitigated by using additional qubits. We show that in
certain situations architectures with considerably slower code cycle times will
still be able to reach desirable run times, provided enough physical qubits are
available. We utilize various space and time optimization strategies that have
been previously considered within the field of error-correcting surface codes.
In particular, we compare two distinct methods of parallelization, Game of
Surface Code's Units, and AutoCCZ factories, both of which enable one to
incrementally speed up the computation until the reaction limited rate is
reached. Finally we calculate the number of physical qubits which would be
required to break the 256 bit elliptic curve encryption of keys in the Bitcoin
network, within the small available time frame in which it would actually pose
a threat to do so. It would require approximately 317 million physical qubits
to break the encryption within one hour using the surface code, a code cycle
time of 1 , a reaction time of 10 , and physical gate error of
. To break the encryption instead within one day it would require 13
million physical qubits.Comment: 22 pages, 4 figure
Versatile ytterbium ion trap experiment for operation of scalable ion-trap chips with motional heating and transition-frequency measurements
We present the design and operation of an ytterbium ion trap experiment with a setup offering versatile optical access and 90 electrical interconnects that can host advanced surface and multilayer ion trap chips mounted on chip carriers. We operate a macroscopic ion trap compatible with this chip carrier design and characterize its performance, demonstrating secular frequencies >1 MHz, and trap and cool nearly all of the stable isotopes, including 171Yb+ ions, as well as ion crystals. For this particular trap we measure the motional heating rate 〈ṅ〉 and observe an 〈ṅ〉∝1/ω2 behavior for different secular frequencies ω. We also determine a spectral noise density SE(1 MHz)=3.6(9)×10-11 V2 m-2 Hz-1 at an ion electrode spacing of 310(10) μm. We describe the experimental setup for trapping and cooling Yb+ ions and provide frequency measurements of the 2S1/2↔2P1/2 and 2D3/2↔3D[3/2]1/2 transitions for the stable 170Yb+, 171Yb+, 172Yb+, 174Yb+, and 176Yb+ isotopes which are more precise than previously published work
Optimal control with a multidimensional quantum invariant
Optimal quantum control of continuous variable systems poses a formidable
computational challenge because of the high-dimensional character of the system
dynamics. The framework of quantum invariants can significantly reduce the
complexity of such problems, but it requires the knowledge of an invariant
compatible with the Hamiltonian of the system in question. We explore the
potential of a Gaussian invariant that is suitable for quadratic Hamiltonians
with any given number of motional degrees of freedom for quantum optimal
control problems that are inspired by current challenges in
ground-state-to-ground-state shuttling of trapped-ions.Comment: 9 pages, 4 figure
Blueprint for a microwave trapped ion quantum computer
The availability of a universal quantum computer may have a fundamental impact on a vast number of research fields and on society as a whole. An increasingly large scientific and industrial community is working toward the realization of such a device. An arbitrarily large quantum computer may best be constructed using a modular approach. We present a blueprint for a trapped ion–based scalable quantum computer module, making it possible to create a scalable quantum computer architecture based on long-wavelength radiation quantum gates. The modules control all operations as stand-alone units, are constructed using silicon microfabrication techniques, and are within reach of current technology. To perform the required quantum computations, the modules make use of long-wavelength radiation–based quantum gate technology. To scale this microwave quantum computer architecture to a large size, we present a fully scalable design that makes use of ion transport between different modules, thereby allowing arbitrarily many modules to be connected to construct a large-scale device. A high error–threshold surface error correction code can be implemented in the proposed architecture to execute fault-tolerant operations. With appropriate adjustments, the proposed modules are also suitable for alternative trapped ion quantum computer architectures, such as schemes using photonic interconnects
Microfabricated Ion Traps
Ion traps offer the opportunity to study fundamental quantum systems with
high level of accuracy highly decoupled from the environment. Individual atomic
ions can be controlled and manipulated with electric fields, cooled to the
ground state of motion with laser cooling and coherently manipulated using
optical and microwave radiation. Microfabricated ion traps hold the advantage
of allowing for smaller trap dimensions and better scalability towards large
ion trap arrays also making them a vital ingredient for next generation quantum
technologies. Here we provide an introduction into the principles and operation
of microfabricated ion traps. We show an overview of material and electrical
considerations which are vital for the design of such trap structures. We
provide guidance in how to choose the appropriate fabrication design, consider
different methods for the fabrication of microfabricated ion traps and discuss
previously realized structures. We also discuss the phenomenon of anomalous
heating of ions within ion traps, which becomes an important factor in the
miniaturization of ion traps
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Quantum computer based on shuttling trapped ions
A microchip-based quantum computer has been built incorporating an architecture in which calculations are carried out by shuttling atomic ions. The device exhibits excellent performance and potential for scaling up