Questions tagged [physical-realization]
For questions about physical implementations of a quantum algorithm or other quantum information protocol. DO NOT use for questions about simulation or emulation of quantum computers, or cloud-based quantum computing services like the IBM Q Experience.
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Physical interpretation of a 2-photon-qubit system occupying the antisymmetric Bell state
This question regards the reconciliation of QIT with what I have learned separately in lectures about quantum physics. My understanding is that indistinguishable bosons are always described by ...
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Hamiltonian in CNOT gate implementation
I am studying the physical implementation of the CNOT gate from "Introduction to Quantum Computing" (Ray LaPierre) and I am confused about the order of operators in the tensor product of the ...
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Does Google's error correction paper invalidate Gil Kalai's arguments?
In his paper "The Argument against Quantum Computers, the Quantum Laws of Nature, and Google’s Supremacy Claims", Gil Kalai argues that quantum advantage will never be reached. For NISQ ...
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Detuning in Rydberg blockade Hamiltonian
I am reading the mechanism of the Rydberg blockade as a quantum gate. For a two-atom system with Rabi frequency $\Omega$, detuning $\Delta$ and blockade potential $V$, the system Hamiltonian is given ...
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Do quantum loops exist?
I was checking the book from Nielsen and Cheng and they mention in chapter 1, page 23, that quantum circuits don't have loops:
"There are a few features allowed in classical circuits that are not ...
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The physical realisation of a quantum oracle [duplicate]
I am having doubts about the physicality of the quantum oracle used in the quantum search algorithms. The standard definition of the search problem (e.g Nielsen and Chuang) states that we are ...
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Changing the phase of one qubit is equivalent to changing the phase of another qubit. What is the physical interpretation of this?
Given two qubits, let's say it's in state $|01\rangle = |0\rangle \otimes |1\rangle$. These two qubits are not entangled.
Applying a $\theta$ angle phase change (sorry if this is the wrong terminology)...
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what is the elementary Lab devices (and their specifications) for building superconducting qubits?
suppose I want to build a superconducting qubit, how can I find the Lab Devices and specifications which are nessecarry to build it?
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What is a gate-level circuit used in the 2022 Jafferis et al. experiment on Sycamore?
A recently published Nature paper of Jafferis et al. describes an experiment with a handful of qubits performed on Google's Sycamore processor to explore the SYK model in the context of AdS/CFT and ...
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Checking if Explanation of Quantum Computer is Correct
My explanation of a quantum computer and why it is potentially faster is below:
A quantum computer uses physical phenomenon to perform operations called gates. These gates act upon things called ...
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Why are quantum systems fabricated to be anharmonic?
I was following the Qiskit textbook:
https://qiskit.org/textbook/ch-quantum-hardware/calibrating-qubits-pulse.html
In this, there is a statement as indicated below:
With superconducting qubits, ...
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Link between binary program output and observable eigenvalue
A quantum cloud server like from IBM typically returns a string of 0's and 1's such as 0010.
An observable such as $Z_1 \otimes Z_2 ... \otimes Z_{n}$ has two eigenvalues +1 or -1. How do I relate ...
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How are measurements done exactly on IBM cloud computers?
A quantum cloud server like from IBM typically returns a string of 0's and 1's such as 0010.
How is this measurement done exactly? I realize that the IBM cloud computers are transmon devices based on ...
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Could a “disco ball” be a good geometry for trapped ion quantum computers?
It seems to me that a good geometry for an ion trap quantum computer would be to constrain the ions to lie on the surface of a sphere. Their mutual repulsion would space them out evenly. If the ions ...
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References discussing the carbon footprint expected for fault-tolerant quantum computers?
There are many problems regarding the scalability of quantum computers, how we need good quantum error correcting codes that scale well and protect well the logical encodings against many possible ...
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Using entropy quantum computing for solving optimization problems
I would like to follow up on this question (What is Entropy Quantum Computing?).
Company Quantum Computing Inc. announced that they made their quantum computer aimed at solving binary optimization ...
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Difference between IBM and Google Quantum Circuit?
I am wondering what the internal differences between IBM and Google quantum circuits are.
They look so different. Google team seems to design their circuit in a fully-connected manner, while the chips ...
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What is entropy quantum computing?
Recently there is news concerning some computational breakthroughs by using so-called "entropy quantum computing":
https://thequantuminsider.com/2022/07/20/qci-solves-3854-variable-problem-...
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Why can two atoms can be entangled?
As a qubit is a two-state (or two-level) quantum-mechanical system, one of the simplest quantum systems displaying the peculiarity of quantum mechanics. Examples include the spin of the electron in ...
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Can the paper by Monz et al. (2015) be regarded as a real implementation of Shor's algorithm?
I'm studying about the Shor algorithm and I wonder whether the paper below can be regarded as a real implementation of the Shor algorithm:
https://arxiv.org/abs/1507.08852
In this paper, they tried to ...
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The world's first quantum integrated circuit at the atomic scale - How does this advance quantum computing as a whole?
I have a hobbyist/enthusiast understanding of Quantum Computing, having read a few books on the subject. I came across this new article and referenced Nature paper. I know a goal of quantum computing ...
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Are there hardware platforms that natively implement parametric two qubit gates?
For example, is it possible to implement RXX gate with an arbitrary angle on an ion computer in a single native operation? The RXX gate with an arbitrary angle can be decomposed into two RXX gates ...
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How are IBM's 127 qubits more potent than the 5760 qubits D-Wave - Advantage_system6.1?
Hi I'm a newbie in quantum computing recently I had a look at the AWS braket and I've seen they had a machine called D-Wave - Advantage_system6.1 that has 5760 qubits but when I googled the highest ...
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Is there the number of CNOT restriction?
I know that there is connectivity restriction when implementing physical CNOT gate.
But, I wonder if there is a limit to the number of physical CNOT gates that can be performed at the same time.
For ...
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The energy levels crossover problem in Quantum Annealing
How to avoid energy levels crossover in quantum annealing by Kibble-Zurek mechanism? Any detailed references?
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Does "detecting and characterizing quantum information [electron spin quantum states]" satisfy statement 5 of DiVincenzo's criteria?
I am reading a company's (Archer Materials) press release on their progress towards building a quantum computing chip and I have a question about how a certain statements are phrased:
Archer’s 12CQ ...
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Is there a toy oracle to show the feasibility of Grover's algorithm?
Is there any small 'toy' oracle that can show the feasibility of Grover's algorithm for searching (without using the geometric rotation interpretation)?
It is confusing that we cannot know the ...
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Do quantum states with a single parameter give any theoretical or experimental advantage compared to multi-parameter ones?
If a quantum state is a single parameter two-qubit mixed entangled state then is there any theoretical or experimental advantage compared to a multi-parameter state?
suppose, we take a single ...
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Experience on analog chaos based qc?
Any expirience on applied analog qc using a chaos based approach. By chaos I mean using analog components in chaos state thus changing between a wide range of states simultanously.
The initial work on ...
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What physically limits qubit connectivity in superconducting chips?
All the superconducting based quantum computers I'm familiar with have a maximum of 4 nearest neighbors per qubit. Trapped ion architectures seem to be able to drive entangling gates between all pairs ...
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Individual processing of quantum circuit measurment results
When superconducting transmon qubits are measured with a readout pulse, the raw readout signal is demodulated, and results appear as clouds on the IQ plane, with one point in the cloud representing ...
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Why does making a quantum circuit more noise resilient make it easier to simulate classically?
I was reading Quantum Computing in the NISQ era and beyond (John Preskill, 2018) but I didn't get this point on pages 9-10:
There is a substantial opportunity for experimentalists and theorists, ...
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How do we know that a superconducting circuit is a quantum system?
In introductions to superconducting qubits, we often take the classical LC circuit and then quantize the operators. Why are we allowed to do this?
I do not see this derivation anywhere -- what ...
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How are gates implemented in a transmon qubit?
A transmon qubit is fundamentally in LC circuit. How are gates implemented in a transmon qubit? How do we know what voltage corresponds to the $\sigma_x$ gate for example?
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In a transmon qubit, what corresponds to the ground and excited states?
In a transmon qubit, we have ground and energy eigenstates but what is actually happening in the circuit here? How do the current and voltage look?
It looks like its made up of things you would find ...
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What are the typical gate times for single-qubit and 2-qubit gates for ion trap, superconducting, neutral atom, photonic, spin QC?
What are the typical gate times for single-qubit and 2-qubit gates for
-- ion trap,
-- superconducting,
-- neutral atom,
-- photonic,
-- spin
quantum computers based on today's technologies?
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How many physical qubits are needed to encode a logical qubit on ion trap, superconducting, neutral atom, photonic QC?
How many physical qubits are needed to encode a logical qubit on an
-- ion trap,
-- superconducting,
-- neutral atom,
-- photonic,
-- spin
quantum computer based on today's technologies?
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What are useful abstraction levels for external quantum input/output of quantum computers?
Section "2.2.3 Quantum measurement" in Nielsen&Chuang uses very general measurement axioms:
Postulate 3: Quantum measurements are described by a collection $\{M_m\}$ of measurement ...
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How to implement gate which is like Identity but multiplied on "i"
In my program I need a single qubit processing gate which implements logic like this:
|0> ==> i*|0>
|1> ==> i*|1>
This is like Identity gate but multiplied on "i"
I ...
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What are introductory resources to learn about quantum computing hardware?
I am interested in learning some details of quantum computers inner working, what are the limitation etc. in order to understand quantum computation more. Can some one refer me to some good materials ...
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Quantum communications and "knowledge" of receiving a qubit
Question from a computer scientist (not a physicist).
Imagine two nodes on a quantum network.
Alice sends Bob a qubit in some state of superposition over a quantum channel.
Is Bob able to sense that ...
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What does it mean for a channel to be independent of the input state?
A 2007 paper shows how to construct quantum channels on finite-dimensional Hilbert spaces
$$\sigma=\Phi(\rho)=\sum_i K_i \rho K_i^\dagger,\qquad \sum_i K_i^\dagger K_i=\mathbb{I}$$ for which $\Phi(\...
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Do individual qubits on IBM quantum processors share the same control unit?
I want to investigate the maximum possible parallelism of quantum operations on a specific IBM device (such as the latest heavy-hex architecture), which requires a basic knowledge of their control ...
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How to obtain control and drift Hamiltonians for device in Qiskit?
I would like to play around with Qiskit OpenPulse and the publicly available IBMQ quantum computer that supports OpenPulse. My humble goal is to use Qutip's optimal control libraries to get a pulse ...
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How to formulate Dynamical Decoupling passes in Qiskit to improve result upon circuit execution
First, let me say that I am not familiar with the idea of Dynamical Decoupling. The goal of this question is to understand how to set up a circuit with dynamical decoupling to improve my hardware ...
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How can time crystals be useful in qRAM design?
A time crystal is a phase of a matter which is ordered in time, similar to classical crystals which are ordered spatially. In other words, the structure of a time crystal is ever-changing but with ...
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What is the justification for the use of this arbitrary post-processing vector?
I am reading through this paper which describes the use of a post-processing vector $\vec{c}$ with elements having values of $(-1,0,1)$. In equation 3 they give their solution as a linear combination ...
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Does QRNG generates True Random numbers?
I read an article that claims, QRNG can produce a true random number. So I wonder, how could they prove that this is a true random numbers generator? In fact, imagine I look at my memory state and ...
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Why do we have to measure the circuit before sending it to the real quantum computer?
If I want to run a circuit on a real quantum computer, I have to measure it before running it. For example:
...
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What type of tasks it is possible to solve on a quantum simulator?
In this article, the author claimed that researches from Harvard and MIT created 256 qubits quantum simulator. However, we are not talking about piece of software on a classical computer but actual ...
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