Questions tagged [physical-qubit]

For questions related to physical realizations of quantum bits i.e. quantum systems living in a 2-dimensional Hilbert space.

19 questions with no upvoted or accepted answers
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What design considerations set the frequency bounds for superconducting qubits?

Superconducting qubits generally have frequencies within the range of 4 - 8 GHz. What design considerations give the upper and lower bounds for what is a feasible design. I.e, why can't they be higher ...
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206 views

What is the charging energy in relation to a superconducting transmon?

The transmon achieves its reduced sensitivity to charge noise by significantly increasing the ratio of the Josephson energy to the charging energy. What is this charging energy?
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30 views

How to design a RF-SQUID qubit by Qiskit Metal?

I am now learning how to use Qiskit Metal to design superconducting circuits. I found that there are only several transmon qubits in the library. Can I design an RF-SQUID qubit by using Qiskit metal? ...
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26 views

Clean way of approximating an oscillator by a qubit

Let me consider a (quantum) Harmonic oscillator of (bare) Hamiltonian: $$H_0=\frac{p^2}{2m}+\frac{1}{2} m \omega^2 x^2$$ (I can add to it an anharmonicity $V=\alpha x^4$ if necessary for the purpose ...
3
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0answers
273 views

What is the difference between a cooper pair box and a transmon qubit?

These two kinds of qubits are both classified under "charge qubits", looking for them, I always find the same circuit representation. Occasionally, I find one where there's a SQUID instead of the ...
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44 views

Excitation of a superconducting circuit

What do we mean by exciting a superconducting circuit--which represent a qubit, how they are get excited inside? how the two states of the qubit are represented in this circuit?
3
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75 views

States of a qubit in a DC-SQUID

Does anybody of you know what are the two states $|0\rangle$ and $|1\rangle$ of a qubit in a DC-SQUID (2 Josephson junctions in a loop)?
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34 views

How much power do quantum computers use based on the number of qubits being allocated?

How much power do quantum computers use based on the number of qubits being allocated? If it's not based on qubits, What determines how much power quantum computers use? Note: A similar question was ...
3
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30 views

Can one make NV centred type qubits from analogus materials in the periodic table?

Can one replace Nitrogen with Phosphorus and Carbon with Silicon and so on? What would be the conditions that would preclude such a realisation? Are there any implemenations so far?
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14 views

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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15 views

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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55 views

I thought we had already passed this error and qubit threshold?

As outlined in Quantum Computing Progress and Prospects published this year, on page 169-171 there is the diagram showing that we are at the 10's of qubits mark. Looking into the diagram further there ...
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77 views

What noise channel that is not coming from the control can lead to XY qubit rotations?

In a semiclassical treatment, the noise Hamiltonian of a quantum system can be treated as a summation over its noise channels in the following way: $$\hat{H}_{\text{noise}}=\sum_{k}\beta_{k}\left(t\...
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27 views

Hamiltonian of the valence electron of Yb+ ion

Let's say I have chosen the valence electron of Yb+ as my qubit. I want to consider it's hyperfine structure as the two-level energy states. Are my following assumptions correct? If the magnetic ...
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21 views

What are the natural, synthetic, identical, heterogeneous qubits? Can anyone explain with examples?

I am reading a paper from 2016, "Quantum computing with atomic qubits and Rydberg interactions: Progress and challenges", In section 2.1, a debate on whether identical or heterogeneous ...
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14 views

What is the role of Josephson junctions and biases in the D-Wave qubit structure?

On the D-Wave 2000Q there are up to 2048 qubits and 5600 coupler. A commonly used picture of one of such qubits is attached below. Each qubit is realized by a loop of niobium controlled by Josephson ...
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51 views

How qubit phase is build in real hardware?

How qubit phase is build in real hardware? On IBM Quantum, D-Wave, etc?
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88 views

Charge Qubit vs Transmon

I want to know the big difference, in terms of fabrication (circuit) between a charge Qubit and a Transmon, how is a Transmon less affected by noise ? Many thanks
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7 views

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 ...