Qube Research & Technologies Technical Interview

The Qube Research & Technologies Technical Interview is stage 2 of 3 in the Qube Research & Technologies interview process, after the Online Assessment. Format: Coding + probability/statistics · candidate-reported. Coding (DS/algos): design and justify a matrix class; two missing numbers in 1..k+2; fewest moves-to-back keeping prefix sums nonnegative; single-edit string transforms.

What the Technical Interview tests

Quant probability/stats: XOR of a fair and a two-headed coin; P(sum of 100 dice > 400) via CLT; correlated standard normals (Corr 0.5): P(X > 3Y), P(X > 3Y | X > 0).

QuantVault maps 11 practice problems to this round. By topic, the biggest groups are coding (7), probability (3), expectation (1); by difficulty, 4 easy, 6 medium and 1 hard. 10 of them were reported by candidates who interviewed at Qube Research & Technologies, most recently in Jul 2026.

• Two to five interviews of about 45 minutes with junior then senior researchers on regression, ML, probability and your CV.
• Reported ML theory includes random forests and their variance, random forest versus XGBoost, ridge and lasso, and positive semidefinite matrices.
• Known question types: the product of the two regression slopes (y on x and x on y) and counting trading paths from flat to a given position.

How to prepare for the Technical Interview

• Correlated normals: write Y = ρX + √(1−ρ²)Z. P(X > 3Y) reduces to a linear combination of independent normals being positive — compute the sign probability via the resulting normal's mean/variance; the conditioning on X > 0 is a bivariate-normal quadrant argument.
• P(sum of 100 dice > 400): mean 350, variance 100·; standardize and use the normal tail. Know the numbers cold.
• Prefix-sum-nonnegative: greedily move the most-negative-contributing elements to the back — reason about why a heap of the smallest prefix contributors is optimal.
• Justify your matrix data structure (flat contiguous array + row-major indexing for cache locality vs. list-of-lists) — they want the property you exploit, not just the choice.

Further reading: How quant superdays work · Behavioral questions at trading firms · Market-making game interview guide.

Question types in this round

The 3 largest question types in the Qube Research & Technologies Technical Interview practice set; across them the most common sub-topics are arrays, bit manipulation, conditional probability, discrete probability, greedy, heap. The questions themselves, with worked solutions, are in the round practice.

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