Pub Date : 2024-04-23DOI: 10.1038/s41534-024-00835-8
Xiao-Ming Zhang, Xiao Yuan
How to efficiently encode classical data is a fundamental task in quantum computing. While many existing works treat classical data encoding as a black box in oracle-based quantum algorithms, their explicit constructions are crucial for the efficiency of practical algorithm implementations. Here, we unveil the mystery of the classical data encoding black box and study the Clifford + T complexity in constructing several typical quantum access models. For general matrices (even including sparse ones), we prove that sparse-access input models and block-encoding both require nearly linear circuit complexities relative to the matrix dimension. We also give construction protocols achieving near-optimal gate complexities. On the other hand, the construction becomes efficient with respect to the data qubit when the matrix is a linear combination of polynomial terms of efficiently implementable unitaries. As a typical example, we propose improved block-encoding when these unitaries are Pauli strings. Our protocols are built upon improved quantum state preparation and a select oracle for Pauli strings, which hold independent values. Our access model constructions provide considerable flexibility, allowing for tunable ancillary qubit numbers and offering corresponding space-time trade-offs.
如何高效地编码经典数据是量子计算的一项基本任务。虽然现有的许多著作都把经典数据编码视为基于甲骨文的量子算法中的黑箱,但它们的明确构造对于实际算法实现的效率至关重要。在这里,我们揭开了经典数据编码黑箱的神秘面纱,并研究了构建几种典型量子访问模型的克利福德 + T 复杂性。对于一般矩阵(甚至包括稀疏矩阵),我们证明稀疏访问输入模型和块编码都需要相对于矩阵维度近乎线性的电路复杂度。我们还给出了实现接近最优门复杂度的构造协议。另一方面,当矩阵是可有效实现的单元的多项式的线性组合时,相对于数据量子比特,构造变得高效。作为一个典型的例子,当这些单元是保利弦时,我们提出了改进的块编码。我们的协议建立在改进的量子态准备和保利弦选择谕令的基础上,保利弦拥有独立的值。我们的访问模型构造具有相当大的灵活性,允许可调的辅助量子比特数,并提供相应的时空权衡。
{"title":"Circuit complexity of quantum access models for encoding classical data","authors":"Xiao-Ming Zhang, Xiao Yuan","doi":"10.1038/s41534-024-00835-8","DOIUrl":"https://doi.org/10.1038/s41534-024-00835-8","url":null,"abstract":"<p>How to efficiently encode classical data is a fundamental task in quantum computing. While many existing works treat classical data encoding as a black box in oracle-based quantum algorithms, their explicit constructions are crucial for the efficiency of practical algorithm implementations. Here, we unveil the mystery of the classical data encoding black box and study the Clifford + <i>T</i> complexity in constructing several typical quantum access models. For general matrices (even including sparse ones), we prove that sparse-access input models and block-encoding both require nearly linear circuit complexities relative to the matrix dimension. We also give construction protocols achieving near-optimal gate complexities. On the other hand, the construction becomes efficient with respect to the data qubit when the matrix is a linear combination of polynomial terms of efficiently implementable unitaries. As a typical example, we propose improved block-encoding when these unitaries are Pauli strings. Our protocols are built upon improved quantum state preparation and a select oracle for Pauli strings, which hold independent values. Our access model constructions provide considerable flexibility, allowing for tunable ancillary qubit numbers and offering corresponding space-time trade-offs.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140639718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-23DOI: 10.1038/s41534-024-00838-5
Claudio Bonizzoni, Alberto Ghirri, Fabio Santanni, Marco Affronte
Spins are prototypical systems with the potential to probe magnetic fields down to the atomic scale limit. Exploiting their quantum nature through appropriate sensing protocols allows to enlarge their applicability to fields not always accessible by classical sensors. Here we first show that quantum sensing protocols for AC magnetic fields can be implemented with molecular spin ensembles embedded into hybrid quantum circuits. We then show that, using only echo detection at microwave frequency and no optical readout, Dynamical Decoupling protocols synchronized with the AC magnetic fields can enhance sensitivity up to S ≈ 10−10 − 10−9 T Hz−1/2 with a low (4-5) number of applied pulses. These results paves the way for the development of strategies to exploit molecular spins as quantum sensors.
自旋是一种典型的系统,具有探测低至原子尺度极限磁场的潜力。通过适当的传感协议利用它们的量子特性,可以将它们的适用范围扩大到经典传感器无法触及的领域。在这里,我们首先展示了交流磁场的量子传感协议可以通过嵌入混合量子电路的分子自旋组合来实现。然后,我们证明,只使用微波频率回波检测而不使用光学读出,与交流磁场同步的动态解耦协议可以在应用脉冲数较少(4-5 个)的情况下将灵敏度提高到 S ≈ 10-10 - 10-9 T Hz-1/2。这些结果为开发利用分子自旋作为量子传感器的策略铺平了道路。
{"title":"Quantum sensing of magnetic fields with molecular spins","authors":"Claudio Bonizzoni, Alberto Ghirri, Fabio Santanni, Marco Affronte","doi":"10.1038/s41534-024-00838-5","DOIUrl":"https://doi.org/10.1038/s41534-024-00838-5","url":null,"abstract":"<p>Spins are prototypical systems with the potential to probe magnetic fields down to the atomic scale limit. Exploiting their quantum nature through appropriate sensing protocols allows to enlarge their applicability to fields not always accessible by classical sensors. Here we first show that quantum sensing protocols for AC magnetic fields can be implemented with molecular spin ensembles embedded into hybrid quantum circuits. We then show that, using only echo detection at microwave frequency and no optical readout, Dynamical Decoupling protocols synchronized with the AC magnetic fields can enhance sensitivity up to <i>S</i> ≈ 10<sup>−10</sup> − 10<sup>−9</sup> T Hz<sup>−1/2</sup> with a low (4-5) number of applied pulses. These results paves the way for the development of strategies to exploit molecular spins as quantum sensors.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140637667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-17DOI: 10.1038/s41534-024-00832-x
Arthur Braida, Simon Martiel, Ioan Todinca
Quantum annealing (QA) holds promise for optimization problems in quantum computing, especially for combinatorial optimization. This analog framework attracts attention for its potential to address complex problems. Its gate-based homologous, QAOA with proven performance, has attracted a lot of attention to the NISQ era. Several numerical benchmarks try to compare these two metaheuristics, however, classical computational power highly limits the performance insights. In this work, we introduce a parametrized version of QA enabling a precise 1-local analysis of the algorithm. We develop a tight Lieb–Robinson bound for regular graphs, achieving the best-known numerical value to analyze QA locally. Studying MaxCut over cubic graph as a benchmark optimization problem, we show that a linear-schedule QA with a 1-local analysis achieves an approximation ratio over 0.7020, outperforming any known 1-local algorithms.
{"title":"Tight Lieb–Robinson Bound for approximation ratio in quantum annealing","authors":"Arthur Braida, Simon Martiel, Ioan Todinca","doi":"10.1038/s41534-024-00832-x","DOIUrl":"https://doi.org/10.1038/s41534-024-00832-x","url":null,"abstract":"<p>Quantum annealing (QA) holds promise for optimization problems in quantum computing, especially for combinatorial optimization. This analog framework attracts attention for its potential to address complex problems. Its gate-based homologous, QAOA with proven performance, has attracted a lot of attention to the NISQ era. Several numerical benchmarks try to compare these two metaheuristics, however, classical computational power highly limits the performance insights. In this work, we introduce a parametrized version of QA enabling a precise 1-local analysis of the algorithm. We develop a tight Lieb–Robinson bound for regular graphs, achieving the best-known numerical value to analyze QA locally. Studying MaxCut over cubic graph as a benchmark optimization problem, we show that a linear-schedule QA with a 1-local analysis achieves an approximation ratio over 0.7020, outperforming any known 1-local algorithms.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-04-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140603633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-16DOI: 10.1038/s41534-024-00836-7
Bujiao Wu, Dax Enshan Koh
Efficiently estimating fermionic Hamiltonian expectation values is vital for simulating various physical systems. Classical shadow (CS) algorithms offer a solution by reducing the number of quantum state copies needed, but noise in quantum devices poses challenges. We propose an error-mitigated CS algorithm assuming gate-independent, time-stationary, and Markovian (GTM) noise. For n-qubit systems, our algorithm, which employs the easily prepared initial state (leftvert {0}^{n}rightrangle ,leftlangle {0}^{n}rightvert) assumed to be noiseless, efficiently estimates k-RDMs with (widetilde{{{{mathcal{O}}}}}(k{n}^{k})) state copies and (widetilde{{{{mathcal{O}}}}}(sqrt{n})) calibration measurements for GTM noise with constant fidelities. We show that our algorithm is robust against noise types like depolarizing, damping, and X-rotation noise with constant strengths, showing scalings akin to prior CS algorithms for fermions but with better noise resilience. Numerical simulations confirm our algorithm’s efficacy in noisy settings, suggesting its viability for near-term quantum devices.
{"title":"Error-mitigated fermionic classical shadows on noisy quantum devices","authors":"Bujiao Wu, Dax Enshan Koh","doi":"10.1038/s41534-024-00836-7","DOIUrl":"https://doi.org/10.1038/s41534-024-00836-7","url":null,"abstract":"<p>Efficiently estimating fermionic Hamiltonian expectation values is vital for simulating various physical systems. Classical shadow (CS) algorithms offer a solution by reducing the number of quantum state copies needed, but noise in quantum devices poses challenges. We propose an error-mitigated CS algorithm assuming gate-independent, time-stationary, and Markovian (GTM) noise. For <i>n</i>-qubit systems, our algorithm, which employs the easily prepared initial state <span>(leftvert {0}^{n}rightrangle ,leftlangle {0}^{n}rightvert)</span> assumed to be noiseless, efficiently estimates <i>k</i>-RDMs with <span>(widetilde{{{{mathcal{O}}}}}(k{n}^{k}))</span> state copies and <span>(widetilde{{{{mathcal{O}}}}}(sqrt{n}))</span> calibration measurements for GTM noise with constant fidelities. We show that our algorithm is robust against noise types like depolarizing, damping, and <i>X</i>-rotation noise with constant strengths, showing scalings akin to prior CS algorithms for fermions but with better noise resilience. Numerical simulations confirm our algorithm’s efficacy in noisy settings, suggesting its viability for near-term quantum devices.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140603943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-12DOI: 10.1038/s41534-024-00837-6
Arash Riazi, Eric Y. Zhu, Dan Xu, Li Qian
Quantum information is often carried in the frequency and polarization degrees of freedom (DoFs) in single photons and entangled photons. We demonstrate an approach to couple and decouple the frequency and polarization DoFs of broadband biphotons. Our approach is based on a nonlinear interferometer consisting of a linear dispersive medium and a polarization controller in between the two biphoton sources (nonlinear media). When the two DoFs are decoupled, maximally polarization-entangled biphotons are observed in the polarization DoF, while interference fringes are observed in the spectrum of the biphotons. When the two DoFs are coupled, by adjusting the polarization controller, interference fringes disappear from the spectrum and instead appear in the degree of polarization entanglement, varying between 0 and 1, depending on the signal and idler frequencies. Our approach offers a convenient means of tuning the polarization entanglement and can be employed for arbitrary biphoton polarization state generation.
{"title":"Entangling entanglement: coupling frequency and polarization of biphotons on demand","authors":"Arash Riazi, Eric Y. Zhu, Dan Xu, Li Qian","doi":"10.1038/s41534-024-00837-6","DOIUrl":"https://doi.org/10.1038/s41534-024-00837-6","url":null,"abstract":"<p>Quantum information is often carried in the frequency and polarization degrees of freedom (DoFs) in single photons and entangled photons. We demonstrate an approach to couple and decouple the frequency and polarization DoFs of broadband biphotons. Our approach is based on a nonlinear interferometer consisting of a linear dispersive medium and a polarization controller in between the two biphoton sources (nonlinear media). When the two DoFs are decoupled, maximally polarization-entangled biphotons are observed in the polarization DoF, while interference fringes are observed in the spectrum of the biphotons. When the two DoFs are coupled, by adjusting the polarization controller, interference fringes disappear from the spectrum and instead appear in the degree of polarization entanglement, varying between 0 and 1, depending on the signal and idler frequencies. Our approach offers a convenient means of tuning the polarization entanglement and can be employed for arbitrary biphoton polarization state generation.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140547433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1038/s41534-024-00833-w
Theodoros Ilias, Dayou Yang, Susana F. Huelga, Martin B. Plenio
We propose and analyze a driven-dissipative quantum sensor that is continuously monitored close to a dissipative critical point. The sensor relies on the critical open Rabi model with the spin and phonon degrees of freedom of a single trapped ion to achieve criticality-enhanced sensitivity. Effective continuous monitoring of the sensor is realized via a co-trapped ancilla ion that switches between dark and bright internal states conditioned on a ‘jump’ of the phonon population which, remarkably, achieves nearly perfect phonon counting despite a low photon collection efficiency. By exploiting both dissipative criticality and efficient continuous readout, the sensor device achieves highly precise sensing of oscillating electric field gradients at a criticality-enhanced precision scaling beyond the standard quantum limit, which we demonstrate is robust to the experimental imperfections in real-world applications.
{"title":"Criticality-enhanced electric field gradient sensor with single trapped ions","authors":"Theodoros Ilias, Dayou Yang, Susana F. Huelga, Martin B. Plenio","doi":"10.1038/s41534-024-00833-w","DOIUrl":"https://doi.org/10.1038/s41534-024-00833-w","url":null,"abstract":"<p>We propose and analyze a driven-dissipative quantum sensor that is continuously monitored close to a dissipative critical point. The sensor relies on the critical open Rabi model with the spin and phonon degrees of freedom of a single trapped ion to achieve criticality-enhanced sensitivity. Effective continuous monitoring of the sensor is realized via a co-trapped ancilla ion that switches between dark and bright internal states conditioned on a ‘jump’ of the phonon population which, remarkably, achieves nearly perfect phonon counting despite a low photon collection efficiency. By exploiting both dissipative criticality and efficient continuous readout, the sensor device achieves highly precise sensing of oscillating electric field gradients at a criticality-enhanced precision scaling beyond the standard quantum limit, which we demonstrate is robust to the experimental imperfections in real-world applications.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140541488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-10DOI: 10.1038/s41534-024-00831-y
Claudio Chamon, Eduardo R. Mucciolo, Andrei E. Ruckenstein, Zhi-Cheng Yang
We propose a mechanism for reaching pseudorandom quantum states, computationally indistinguishable from Haar random, with shallow log-n depth quantum circuits, where n is the number of qudits. We argue that (log n) depth 2-qubit-gate-based generic random quantum circuits that are claimed to provide a lower bound on the speed of information scrambling, cannot produce computationally pseudorandom quantum states. This conclusion is connected with the presence of polynomial (in n) tails in the stay probability of short Pauli strings that survive evolution through such shallow circuits. We show, however, that stay-probability-tails can be eliminated and pseudorandom quantum states can be accomplished with shallow (log n) depth circuits built from a special universal family of “inflationary” quantum (IQ) gates. We prove that IQ-gates cannot be implemented with 2-qubit gates, but can be realized either as a subset of 2-qudit-gates in U(d2) with d ≥ 3 and d prime, or as special 3-qubit gates.
我们提出了一种机制,利用深度为log-n的浅量子电路(其中n为量子比特数)达到伪随机量子态,在计算上与哈尔随机无异。我们认为,据称能提供信息扰乱速度下限的基于2-量子位门的(log n )深度通用随机量子电路无法产生计算上的伪随机量子态。这一结论与通过这种浅层电路进化存活下来的短保利弦的滞留概率存在多项式(n)尾巴有关。然而,我们证明了停留概率尾巴是可以消除的,而且伪随机量子态可以通过由 "膨胀 "量子(IQ)门的一个特殊通用家族构建的浅(log n )深度电路来实现。我们证明了 IQ 门不能用 2 量子门实现,但可以作为 U(d2) 中 d≥3 且 d 为素数的 2 量子门子集实现,或者作为特殊的 3 量子门实现。
{"title":"Fast pseudorandom quantum state generators via inflationary quantum gates","authors":"Claudio Chamon, Eduardo R. Mucciolo, Andrei E. Ruckenstein, Zhi-Cheng Yang","doi":"10.1038/s41534-024-00831-y","DOIUrl":"https://doi.org/10.1038/s41534-024-00831-y","url":null,"abstract":"<p>We propose a mechanism for reaching pseudorandom quantum states, computationally indistinguishable from Haar random, with shallow log-<i>n</i> depth quantum circuits, where <i>n</i> is the number of qudits. We argue that <span>(log n)</span> depth 2-qubit-gate-based generic random quantum circuits that are claimed to provide a lower bound on the speed of information scrambling, cannot produce computationally pseudorandom quantum states. This conclusion is connected with the presence of polynomial (in <i>n</i>) tails in the stay probability of short Pauli strings that survive evolution through such shallow circuits. We show, however, that stay-probability-tails can be eliminated and pseudorandom quantum states can be accomplished with shallow <span>(log n)</span> depth circuits built from a special universal family of “inflationary” quantum (IQ) gates. We prove that IQ-gates cannot be implemented with 2-qubit gates, but can be realized either as a subset of 2-qudit-gates in <i>U</i>(<i>d</i><sup>2</sup>) with <i>d</i> ≥ 3 and <i>d</i> prime, or as special 3-qubit gates.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140547422","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-04DOI: 10.1038/s41534-024-00834-9
Lorcán O. Conlon, Biveen Shajilal, Angus Walsh, Jie Zhao, Jiri Janousek, Ping Koy Lam, Syed M. Assad
Quantum mechanics offers the possibility of unconditionally secure communication between multiple remote parties. Security proofs for such protocols typically rely on bounding the capacity of the quantum channel in use. In a similar manner, Cramér-Rao bounds in quantum metrology place limits on how much information can be extracted from a given quantum state about some unknown parameters of interest. In this work we establish a connection between these two areas. We first demonstrate a three-party sensing protocol, where the attainable precision is dependent on how many parties work together. This protocol is then mapped to a secure access protocol, where only by working together can the parties gain access to some high security asset. Finally, we map the same task to a communication protocol where we demonstrate that a higher mutual information can be achieved when the parties work collaboratively compared to any party working in isolation.
{"title":"Verifying the security of a continuous variable quantum communication protocol via quantum metrology","authors":"Lorcán O. Conlon, Biveen Shajilal, Angus Walsh, Jie Zhao, Jiri Janousek, Ping Koy Lam, Syed M. Assad","doi":"10.1038/s41534-024-00834-9","DOIUrl":"https://doi.org/10.1038/s41534-024-00834-9","url":null,"abstract":"<p>Quantum mechanics offers the possibility of unconditionally secure communication between multiple remote parties. Security proofs for such protocols typically rely on bounding the capacity of the quantum channel in use. In a similar manner, Cramér-Rao bounds in quantum metrology place limits on how much information can be extracted from a given quantum state about some unknown parameters of interest. In this work we establish a connection between these two areas. We first demonstrate a three-party sensing protocol, where the attainable precision is dependent on how many parties work together. This protocol is then mapped to a secure access protocol, where only by working together can the parties gain access to some high security asset. Finally, we map the same task to a communication protocol where we demonstrate that a higher mutual information can be achieved when the parties work collaboratively compared to any party working in isolation.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140349576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Atoms falling into a black hole (BH) through a cavity are shown to enable coherent amplification of light quanta powered by the BH-gravitational vacuum energy. This process can harness the BH energy towards useful purposes, such as propelling a spaceship trapped by the BH. The process can occur via transient amplification of a signal field by falling atoms that are partly excited by Hawking radiation reflected by an orbiting mirror. In the steady-state regime of thermally equilibrated atoms that weakly couple to the field, this amplifier constitutes a BH-powered quantum heat engine. The envisaged effects substantiate the thermodynamic approach to BH acceleration radiation.
{"title":"Black-hole powered quantum coherent amplifier","authors":"Avijit Misra, Pritam Chattopadhyay, Anatoly Svidzinsky, Marlan O. Scully, Gershon Kurizki","doi":"10.1038/s41534-024-00817-w","DOIUrl":"https://doi.org/10.1038/s41534-024-00817-w","url":null,"abstract":"<p>Atoms falling into a black hole (BH) through a cavity are shown to enable coherent amplification of light quanta powered by the BH-gravitational vacuum energy. This process can harness the BH energy towards useful purposes, such as propelling a spaceship trapped by the BH. The process can occur via transient amplification of a signal field by falling atoms that are partly excited by Hawking radiation reflected by an orbiting mirror. In the steady-state regime of thermally equilibrated atoms that weakly couple to the field, this amplifier constitutes a BH-powered quantum heat engine. The envisaged effects substantiate the thermodynamic approach to BH acceleration radiation.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140310791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-27DOI: 10.1038/s41534-024-00827-8
Luis Fabián Peña, Justine C. Koepke, Joseph Houston Dycus, Andrew Mounce, Andrew D. Baczewski, N. Tobias Jacobson, Ezra Bussmann
SiGe heteroepitaxial growth yields pristine host material for quantum dot qubits, but residual interface disorder can lead to qubit-to-qubit variability that might pose an obstacle to reliable SiGe-based quantum computing. By convolving data from scanning tunneling microscopy and high-angle annular dark field scanning transmission electron microscopy, we reconstruct 3D interfacial atomic structure and employ an atomistic multi-valley effective mass theory to quantify qubit spectral variability. The results indicate (1) appreciable valley splitting (VS) variability of ~50% owing to alloy disorder and (2) roughness-induced double-dot detuning bias energy variability of order 1–10 meV depending on well thickness. For measured intermixing, atomic steps have negligible influence on VS, and uncorrelated roughness causes spatially fluctuating energy biases in double-dot detunings potentially incorrectly attributed to charge disorder. Our approach yields atomic structure spanning orders of magnitude larger areas than post-growth microscopy or tomography alone, enabling more holistic predictions of disorder-induced qubit variability.
硅锗异质外延生长为量子点量子比特提供了原始的宿主材料,但残留的界面紊乱会导致量子比特间的变异,这可能会对基于硅锗的可靠量子计算构成障碍。通过融合扫描隧道显微镜和高角度环形暗场扫描透射电子显微镜的数据,我们重建了三维界面原子结构,并采用原子论多谷有效质量理论来量化量子比特光谱变异性。结果表明:(1) 由于合金无序,谷分裂 (VS) 的可观变化约为 50%;(2) 粗糙度引起的双点失谐偏置能量变化约为 1-10 meV,这取决于阱的厚度。对于测量到的混合物,原子阶梯对 VS 的影响可以忽略不计,而不相关的粗糙度会导致双点失谐的空间波动能量偏差,这可能会被错误地归因于电荷失调。与生长后显微镜或层析成像法相比,我们的方法能获得更大范围的原子结构,从而能更全面地预测无序诱导的量子比特变异性。
{"title":"Modeling Si/SiGe quantum dot variability induced by interface disorder reconstructed from multiperspective microscopy","authors":"Luis Fabián Peña, Justine C. Koepke, Joseph Houston Dycus, Andrew Mounce, Andrew D. Baczewski, N. Tobias Jacobson, Ezra Bussmann","doi":"10.1038/s41534-024-00827-8","DOIUrl":"https://doi.org/10.1038/s41534-024-00827-8","url":null,"abstract":"<p>SiGe heteroepitaxial growth yields pristine host material for quantum dot qubits, but residual interface disorder can lead to qubit-to-qubit variability that might pose an obstacle to reliable SiGe-based quantum computing. By convolving data from scanning tunneling microscopy and high-angle annular dark field scanning transmission electron microscopy, we reconstruct 3D interfacial atomic structure and employ an atomistic multi-valley effective mass theory to quantify qubit spectral variability. The results indicate (1) appreciable valley splitting (VS) variability of ~50% owing to alloy disorder and (2) roughness-induced double-dot detuning bias energy variability of order 1–10 meV depending on well thickness. For measured intermixing, atomic steps have negligible influence on VS, and uncorrelated roughness causes spatially fluctuating energy biases in double-dot detunings potentially incorrectly attributed to charge disorder. Our approach yields atomic structure spanning orders of magnitude larger areas than post-growth microscopy or tomography alone, enabling more holistic predictions of disorder-induced qubit variability.</p>","PeriodicalId":19212,"journal":{"name":"npj Quantum Information","volume":null,"pages":null},"PeriodicalIF":7.6,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140310771","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}