We report a quantum simulation of the deuteron binding energy on quantum processors accessed via cloud servers. We use a Hamiltonian from pionless effective field theory at leading order. We design a ...low-depth version of the unitary coupled-cluster ansatz, use the variational quantum eigensolver algorithm, and compute the binding energy to within a few percent. Our work is the first step towards scalable nuclear structure computations on a quantum processor via the cloud, and it sheds light on how to map scientific computing applications onto nascent quantum devices.
We present a quantum-classical algorithm to study the dynamics of the two-spatial-site Schwinger model on IBM's quantum computers. Using rotational symmetries, total charge, and parity, the number of ...qubits needed to perform computation is reduced by a factor of ~5, removing exponentially large unphysical sectors from the Hilbert space. Our work opens an avenue for exploration of other lattice quantum field theories, such as quantum chromodynamics, where classical computation is used to find symmetry sectors in which the quantum computer evaluates the dynamics of quantum fluctuations.
We present and demonstrate a novel protocol for distributing secret keys between two and only two parties based on N-party single-qubit Quantum Secret Sharing (QSS). We demonstrate our new protocol ...with N = 3 parties using phase-encoded photons. We show that any two out of N parties can build a secret key based on partial information from each other and with collaboration from the remaining N - 2 parties. Our implementation allows for an accessible transition between N-party QSS and arbitrary two party QKD without modification of hardware. In addition, our approach significantly reduces the number of resources such as single photon detectors, lasers and dark fiber connections needed to implement QKD.
Purpose: Biological treatment planning based on the equivalent uniform dose (EUD) demonstrates reduced treatment toxicity and better tumor control. However, EUD based approaches are lacking tools for ...controlling and refining resultant dose distributions on a voxel level. Here we introduce a method enabling regional dose distribution manipulations for biological IMRT treatment planning. Method and Materials: Two dose distributions with the same EUD are EUD equivalent. However, one might be more clinically acceptable than the other. Embedding tools that find clinically more acceptable solutions and allow dose refining into biologic optimization is thus very important. We propose to use a hybrid biologic/physical dose optimization approach. We first identify region(s) where dose refinement is desired. For them a quadratic dose‐volume objective function with a homogeneous prescription is formulated. The remaining structures are included into the planning via EUD dose constraints. If the resultant optimal dose distribution does not fulfill planner's clinical dose‐volume criteria then the prescription is adjusted and the problem is re‐optimized. The adjustment mechanism accounts for the intrinsic dosimetric inequality between voxels which is ignored by the EUD and the objective function. Results: A clinical prostate case was used to test our method. The PTV was selected as a primary target for dose refinement. The rectum and the bladder were incorporated into the optimization via EUD constraints. By adjusting voxel prescriptions in the PTV iteratively, a dose improvement was obtained for the PTV and dose reduction was achieved in the critical structures comparing to a conventional dose‐volume based objective plan with the same PTV coverage. For instance, we demonstrate up to 25% reduction in the mean dose to the rectum. Conclusions: We show that regional dose distribution control and refinement can be achieved for biological optimization. It is relevant in the context of 3D dose sculpting based on the EUD.
Purpose: To incorporate patient‐specific spatially‐dependent prescription dose selection and optimization into IMRT inverse treatment planning. To improve the quality of planning using customized ...variable prescription. Method and Materials: The standard prescription dose—100% of the dose to 100% of the target volume and 0% to the rest of structures—is not achievable in practice. A more realistic prescription dose distribution would be a voxel specific prescription which can be automatically tuned during optimization procedure. One of the ways to realize that in practice is to think about prescription as it were a random variable with some restrictions on its probability distribution function (PDF) which plays the role of a preference function guiding optimization process. We demonstrate that, under the assumption that the prescription dose obeys a normal distribution, IMRT planning with random prescription can be formulated as a quadratic problem. Results: Clinical prostate and head and neck cases were studied to test this method. We compare treatment plans generated using this method to standard prescription plans for the same sets of importance factors. Depending on model parameter values improved plans were generated using the randomized prescription. Larger improvements were observed for the prostate case which may indicate that our technique works the best when the target is closely surrounded by organs at risk. Conclusions: We demonstrated how IMRT treatment planning can be improved via considering customized prescription dose.
Purpose: To devise a technique to improve tumor (organ) dose distribution and reduce under and overdosing in IMRT planning by means of iterative adjustment of voxel‐specific prescription doses. ...Method and Materials: We use a spatially‐dependent penalty scheme based on how well a given voxel satisfies its ideal clinical prescriptions. In this situation both under‐dosed and overdosed voxels are penalized with a penalty weight proportional to the amount of the dose departure from the ideal prescription. Alternatively, the method can be interpreted as the iterative adjustment of individual voxel prescriptions in order to produce an improved dose distribution. If a voxel is over (under) dosed then its prescription dose is decreased (increased) and the plan is re‐optimized. The procedure is repeated until voxel's dose cannot be improved anymore. Remarkably, guided by a metric such as a dose‐volume histogram (DVH), our method is capable of producing significantly improved treatment plans iteratively without expert's intervention. Results: A clinical head and neck case was used to test this method. By adjusting voxel prescriptions to compensate for the inequalities between the actual calculated and desired doses, substantial improvements are obtained for the treatment plan as large dose reductions were achieved in almost all of the critical structures present. For instance, we demonstrate fivefold reduction in the maximum dose to the brainstem. Other organs at risk experience dose reduction ranging from 100 to 300 percents. Conclusions: Our method can readily be implemented with any treatment planning system and demonstrates fast convergence and significantly improved plans.
We present a method of measuring expectation values of quadrature moments of a multimode field through two-level probe “homodyning”. Our approach is based on an integral transform formalism of ...measurable probe observables, where analytically derived kernels unravel efficiently the required field information at zero interaction time, minimizing decoherence effects. The proposed scheme is suitable for fields that, while inaccessible to a direct measurement, enjoy one and two-photon Jaynes-Cummings interactions with a two-level probe, like spin, phonon, or cavity fields. Available data from previous experiments are used to confirm our predictions.
We present an operational definition of the Wigner function. Our method relies on the Fresnel transform of measured Rabi oscillations and applies to motional states of trapped atoms as well as to ...field states in cavities. We illustrate this technique using data from recent experiments in ion traps Phys. Rev. Lett. 76, 1796 (1996) and in cavity QED Nature (London) 403, 743 (2000). The values of the Wigner functions of the underlying states at the origin of phase space are W(|0>)(0)=+1.75 for the vibrational ground state and W(|1>)(0)=-1.4 for the one-photon number state. We generalize this method to wave packets in arbitrary potentials.
In this paper we show how ground-state coherences and dispersive interactions of single photons with a collective system produces a variety of multiparticle entangled states and mesoscopic ...superpositions. Further single photons act as a carrier of information and can entangle macroscopic systems and can produce large phase shifts. Our work produces states as considered by Schrödinger in the cat-paradox, though in our case cat is replaced by the collective atomic system.
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