37 research outputs found
Magic-State Functional Units: Mapping and Scheduling Multi-Level Distillation Circuits for Fault-Tolerant Quantum Architectures
Quantum computers have recently made great strides and are on a long-term
path towards useful fault-tolerant computation. A dominant overhead in
fault-tolerant quantum computation is the production of high-fidelity encoded
qubits, called magic states, which enable reliable error-corrected computation.
We present the first detailed designs of hardware functional units that
implement space-time optimized magic-state factories for surface code
error-corrected machines. Interactions among distant qubits require surface
code braids (physical pathways on chip) which must be routed. Magic-state
factories are circuits comprised of a complex set of braids that is more
difficult to route than quantum circuits considered in previous work [1]. This
paper explores the impact of scheduling techniques, such as gate reordering and
qubit renaming, and we propose two novel mapping techniques: braid repulsion
and dipole moment braid rotation. We combine these techniques with graph
partitioning and community detection algorithms, and further introduce a
stitching algorithm for mapping subgraphs onto a physical machine. Our results
show a factor of 5.64 reduction in space-time volume compared to the best-known
previous designs for magic-state factories.Comment: 13 pages, 10 figure
Resource Optimized Quantum Architectures for Surface Code Implementations of Magic-State Distillation
Quantum computers capable of solving classically intractable problems are
under construction, and intermediate-scale devices are approaching completion.
Current efforts to design large-scale devices require allocating immense
resources to error correction, with the majority dedicated to the production of
high-fidelity ancillary states known as magic-states. Leading techniques focus
on dedicating a large, contiguous region of the processor as a single
"magic-state distillation factory" responsible for meeting the magic-state
demands of applications. In this work we design and analyze a set of optimized
factory architectural layouts that divide a single factory into spatially
distributed factories located throughout the processor. We find that
distributed factory architectures minimize the space-time volume overhead
imposed by distillation. Additionally, we find that the number of distributed
components in each optimal configuration is sensitive to application
characteristics and underlying physical device error rates. More specifically,
we find that the rate at which T-gates are demanded by an application has a
significant impact on the optimal distillation architecture. We develop an
optimization procedure that discovers the optimal number of factory
distillation rounds and number of output magic states per factory, as well as
an overall system architecture that interacts with the factories. This yields
between a 10x and 20x resource reduction compared to commonly accepted single
factory designs. Performance is analyzed across representative application
classes such as quantum simulation and quantum chemistry.Comment: 16 pages, 14 figure
Hardware Architecture for a Quantum Computer Trusted Execution Environment
The cloud-based environments in which today's and future quantum computers
will operate, raise concerns about the security and privacy of user's
intellectual property. Quantum circuits submitted to cloud-based quantum
computer providers represent sensitive or proprietary algorithms developed by
users that need protection. Further, input data is hard-coded into the
circuits, and leakage of the circuits can expose users' data. To help protect
users' circuits and data from possibly malicious quantum computer cloud
providers, this work presented the first hardware architecture for a trusted
execution environment for quantum computers. To protect the user's circuits and
data, the quantum computer control pulses are obfuscated with decoy control
pulses. While digital data can be encrypted, analog control pulses cannot and
this paper proposed the novel decoy pulse approach to obfuscate the analog
control pulses. The proposed decoy pulses can easily be added to the software
by users. Meanwhile, the hardware components of the architecture proposed in
this paper take care of eliminating, i.e. attenuating, the decoy pulses inside
the superconducting quantum computer's dilution refrigerator before they reach
the qubits. The hardware architecture also contains tamper-resistant features
to protect the trusted hardware and users' information. The work leverages a
new metric of variational distance to analyze the impact and scalability of
hardware protection. The variational distance of the circuits protected with
our scheme, compared to unprotected circuits, is in the range of only to
. This work demonstrates that protection from possibly malicious cloud
providers is feasible and all the hardware components needed for the proposed
architecture are available today
SQUARE: Strategic Quantum Ancilla Reuse for Modular Quantum Programs via Cost-Effective Uncomputation
Compiling high-level quantum programs to machines that are size constrained
(i.e. limited number of quantum bits) and time constrained (i.e. limited number
of quantum operations) is challenging. In this paper, we present SQUARE
(Strategic QUantum Ancilla REuse), a compilation infrastructure that tackles
allocation and reclamation of scratch qubits (called ancilla) in modular
quantum programs. At its core, SQUARE strategically performs uncomputation to
create opportunities for qubit reuse.
Current Noisy Intermediate-Scale Quantum (NISQ) computers and forward-looking
Fault-Tolerant (FT) quantum computers have fundamentally different constraints
such as data locality, instruction parallelism, and communication overhead. Our
heuristic-based ancilla-reuse algorithm balances these considerations and fits
computations into resource-constrained NISQ or FT quantum machines, throttling
parallelism when necessary. To precisely capture the workload of a program, we
propose an improved metric, the "active quantum volume," and use this metric to
evaluate the effectiveness of our algorithm. Our results show that SQUARE
improves the average success rate of NISQ applications by 1.47X. Surprisingly,
the additional gates for uncomputation create ancilla with better locality, and
result in substantially fewer swap gates and less gate noise overall. SQUARE
also achieves an average reduction of 1.5X (and up to 9.6X) in active quantum
volume for FT machines.Comment: 14 pages, 10 figure
Refractory microsatellite stable metastatic colorectal cancer with ERBB2/ERBB3 mutation may be preferred population for regorafenib plus PD-1 inhibitor therapy: a real-world study
BackgroundMicrosatellite stable (MSS) colorectal cancer (CRC) has been referred to as the “cold tumor” because of almost no response to anti–programmed death-1 (PD-1) antibody. A recent REGONIVO trial showed that regorafenib plus nivolumab had an encouraging efficacy in MSS metastatic CRC (mCRC). However, only a small subset of patients may benefit from the combination therapy. We aim to evaluate the efficacy and safety data of immune checkpoint inhibitors combined with regorafenib in refractory MSS mCRC and to discover biomarkers that can effectively stratify the beneficial patient population.MethodsWe retrospectively analyzed patients with MSS mCRC who received regorafenib combined with anti–PD-1 antibody therapy. The objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and status of gene mutation were reviewed and evaluated.ResultsTwenty-one patients received combination treatment. At a median treatment duration of 4 months, one patient achieved complete response, three patients achieved partial response, and two patients achieved stable disease as the best response. The ORR and DCR were 19% and 28.5% in the overall population, respectively. The median PFS was 4 months, and the median OS was 25 months. Only erbb2 receptor tyrosine kinase 2/erbb3 receptor tyrosine kinase 3 (ERBB2/ERBB3) mutation status was confirmed to be a potential predictive factor for effective treatment. In patients with ERBB2/ERBB3 mutation, ORR, DCR, and PFS exhibited significant improvements in comparison with that in wild-type patients. Grade 3 or higher treatment-related adverse events occurred in three patients (14.3%).ConclusionsRegorafenib in combination with PD-1 inhibitor provides a feasible treatment regimen for refractory MSS mCRC with tolerated toxicity. Patients with ERBB2/ERBB3 mutation may be the preferred population for this combination regimen
PAN: Pulse Ansatz on NISQ Machines
Variational quantum algorithms (VQAs) have demonstrated great potentials in
the NISQ era. In the workflow of VQA, the parameters of ansatz are iteratively
updated to approximate the desired quantum states. We have seen various efforts
to draft better ansatz with less gates. In quantum computers, the gate ansatz
will eventually be transformed into control signals such as microwave pulses on
transmons. And the control pulses need elaborate calibration to minimize the
errors such as over-rotation and under-rotation. In the case of VQAs, this
procedure will introduce redundancy, but the variational properties of VQAs can
naturally handle problems of over-rotation and under-rotation by updating the
amplitude and frequency parameters. Therefore, we propose PAN, a native-pulse
ansatz generator framework for VQAs. We generate native-pulse ansatz with
trainable parameters for amplitudes and frequencies. In our proposed PAN, we
are tuning parametric pulses, which are natively supported on NISQ computers.
Considering that parameter-shift rules do not hold for native-pulse ansatz, we
need to deploy non-gradient optimizers. To constrain the number of parameters
sent to the optimizer, we adopt a progressive way to generate our native-pulse
ansatz. Experiments are conducted on both simulators and quantum devices to
validate our methods. When adopted on NISQ machines, PAN obtained improved the
performance with decreased latency by an average of 86%. PAN is able to achieve
99.336% and 96.482% accuracy for VQE tasks on H2 and HeH+ respectively, even
with considerable noises in NISQ machines.Comment: 13 pages, 13 figure